Samacheer Kalvi 11th Chemistry Solutions Chapter 4 Hydrogen

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Tamilnadu Samacheer Kalvi 11th Chemistry Solutions Chapter 4 Hydrogen

Samacheer Kalvi 11th Chemistry Hydrogen Textual Evaluation Solved

I. Choose The Correct Answer:
Question 1.
Which of the following statements about hydrogen is incorrect ? (NEET – 2016)
(a) Hydrogen ion, H₃O⁺ exists freely in solution.
(b) Dihydrogen acts a,s a reducing agent.
(c) Hydrogen has three isotopes of which tritium is the most common.
(d) Hydrogen never acts as a cation in ionic salts.
Answer:
(c) Hydrogen has three isotopes of which tritium is the most common.
Hint:
Correct statement:
Hydrogen has three isotopes of which protium is the most common.

Question 2.
Water-gas is ………..
(a) H₂ O_(g)
(b) CO + H₂O
(C) CO + H₂
(d) CO + N₂
Answer:
(c) CO + H₂

Question 3.
Which one of the following statements is incorrect with regard to ortho and para dihydrogen?
(a) They are nuclear spin isomers
(b) Ortho isomer has zero nuclear spins whereas the para isomer has one nuclear spin
(c) The para isomer is favoured at low temperatures
(d) The thermal conductivity of the para isomer is 50% greater than that of the ortho isomer.
Answer:
(b) Ortho isomer has zero nuclear spins whereas the para isomer has one nuclear spin
Hints:
Correct statement:
Ortho isomer – one nuclear spin Para isomer – zero nuclear spin

Question 4.
Ionic hydrides are formed by …………….
(a) halogens
(b) chalcogens
(c) inert gases
(d) group one elements
Answer:
(d) group one elements
e.g., Sodium hydride (Na⁺ H^– )

Question 5.
Tritium nucleus is contains ……………..
(a) 1p + 0n
(b) 2p + 1n
(c) 1p + 2n
(d) none of these
Answer:
(c) lp + 2n
₁T³ (le^–, lp, 2n)

Question 6.
Non-stoichiometric hydrides are formed by……………..
(a) palladium, vanadium
(b) carbon, nickel
(c) manganese, lithium
(d) nitrogen, chlorine
Answer:
(a) palladium, vanadium

Question 7.
Assertion: Permanent hardness of water is removed by treatment with washing soda.
Reason: Washing soda reacts with soluble calcium and magnesium chlorides and sulphates in hard water to form insoluble carbonates
(a) Both assertion and reason are true and the reason is the correct explanation of assertion.
(b) Both assertion and reason are true but the reason is not the correct explanation of assertion.
(c) Assertion is true but the reason is false
(d) Both assertion and reason are false
Answer:
(a) Both assertion and reason are true and the reason is the correct explanation of assertion.
Ca²⁺ + Na₂CO₃ → CaCO₃↓ + 2Na⁺

Question 8.
If a body of a fish contains 1.2 g hydrogen in its total body mass, if all the hydrogen is replaced with deuterium then the increase in body weight of the fish will be ……………
(a) 1.2 g
(b) 2.4 g
(c) 3.6 g
(d) \(\sqrt{4.8}\) g
Answer:
(a) 1.2 g
Hints:
Mass of deuterium = 2 × mass of protium
If all the 1.2 g hydrogen is replaced with deuterium, the weight will become 2.4g. Hence the increase in body weight is (2.4 – 1.2 = 1.2 g).

Question 9.
The hardness of water can be determined by volumetrically using the reagent …………..
(a) sodium thiosulphate
(b) potassium permanganate
(c) hydrogen peroxide
(d) EDTA
Answer:
(d) EDTA

Question 10.
The cause of permanent hardness of water is due to ………….
(a) Ca(HCO₃)₂
(b) Mg(HCO_3k)₃
(c) CaCl₂
(d) MgCO₃
Answer:
(c) CaCl₂
Hints:
The permanent hardness of water is due to the presence of the chlorides, nitrates and sulphates of Ca²⁺ and Mg²⁺ ions.

Question 11.
Zeolite used to soften hardness of water is, hydrated ………….
(a) Sodium aluminium silicate
(b) Calcium aluminium silicate
(c) Zinc aluminium borate
(d) Lithium aluminium hydride
Answer:
(a) Sodium aluminium silicate
Zeolite is sodium aluminium silicate.
(NaAlSi₂O₆ .H₂O)

Question 12.
A commercial sample of hydrogen peroxide marked as 100 volume H₂O₂, it means that ……………
(a) 1 ml of H₂O₂ will give 100 ml O₂ at STP
(b) 1 L of H₂O₂ will give 100 ml O₂ at STP
(c) 1 L of H₂O₂ will give 22.4 L O₂
(d) 1 ml of H₂O₂ will give 1 mole of O₂ at STP
Answer:
(a) 1 ml of H₂O₂ will give 100 ml O₂ at STP

Question 13.
When hydrogen peroxide is shaken with an acidified solution of potassium dichromate in presence of ether, the ethereal layer turns blue due to the formation of
(a) Cr₂ O₃
(b) CrO₄^2-
(c) CrO(O₂)₂
(d) none of these
Answer:
(c) CrO(O₂)₂ CrO(O₂)₂
Hints:
Cr₂O₇^2- + 2H⁺ + 4H₂O₂ → 2CrO(O₂)₂ + 5H₂O

Question 14.
For decolorization of 1 mole of acidified KMnO₄, the moles of H₂O₂ required is …………….
(a) \(\frac {1}{2}\)
(b) \(\frac {3}{2}\)
(c) \(\frac {5}{2}\)
(d) \(\frac {7}{2}\)
Answer:
(c) \(\frac {5}{2}\)
Hints:
2MnO₄^– + 5H₂O_2(aq) + 6H⁺ → 2Mn²⁺+ 5O₂ + 8H₂O

Question 15.
Volume strength of 1.5 N H₂O₂ is ……………..
(a) 1.5
(b) 4.5
(c) 16.8
(d) 8.4
Answer:
(d) 8.4
Hints:
Volume strength of hydrogen peroxide = Normality of hydrogen peroxide × 5.6 = 1.5 x 5.6 = 8.4

Volume strength of hydrogen peroxide
= Normality × \(\frac {17 × 22.4}{68}\)
Volume strength of hydrogen peroxide = Normality x 5.6

Question 16.
The hybridization of oxygen atom is H₂O and H₂O₂ are respectively
(a) sp and sp³
(b) sp and sp
(c) sp and sp²
(d) sp3 and sp³
Answer:
(d) sp³ and sp³

Question 17.
The reaction H₃PO₂ + D₂O → H₂DPO₂ + HDO indicates that hypo-phosphorus acid is ……………
(a) tri basic acid
(b) di basic acid
(c) mono basic acid
(d) none of these

Answer:
(c) monobasic acid
Hints:
Hypophosphorous acid on reaction with D₂O, only one hydrogen is replaced P by deuterium and hence it is monobasic.

Question 18.
In solid ice, the oxygen atom is surrounded
(a) tetrahedrally by 4 hydrogen atoms
(b) octahedrally by 2 oxygen and 4 hydrogen atoms
(c) tetrahedrally by 2 hydrogen and 2 oxygen atoms
(d) octahedrally by 6 hydrogen atoms
Answer:
(a) tetrahedrally by 4 hydrogen atoms

Question 19.
The type of H-bonding present in ortho nitrophenol and p-nitrophenol is respectively ……………
(a) intermolecular H-bonding and intramolecular H-bonding
(b) intramolecular H-bonding and intermolecular H-bonding
(c) intramolecular H – bonding and no H – bonding
(d) intramolecular H – bonding and intramolecular H – bonding

Answer:
(A) intramolecular H-bonding and intermolecular H-bonding

Question 20.
Heavy water is used as ……………
(a) modulator in nuclear reactions
(b) coolant in nuclear reactions
(c) both (a) and (b)
(d) none of these
Answer:
(c) both (a) and (A)
Hints:
Heavy water is used as a moderator as well as a coolant in nuclear reactions.

Question 21.
Water is a ……………
(a) basic oxide
(b) acidic oxide
(c) amphoteric oxide
(d) none of these
Answer:
(c) amphoteric oxide

II. Write brief answer to the following questions

Question 22.
Explain why hydrogen is not placed with the halogen in the periodic table.
Answer:
The electron affinity of hydrogen is much less than that of halogen atoms. Hence, the tendency of hydrogen to form hydride ions is low compared to that of halide ions. In most of its compounds hydrogen exists in a +1 oxidation state. Therefore, it is reasonable to place the hydrogen in group -1 along with alkali metals and not placed with halogens.

Question 23.
the cube at 0°C is placed in some liquid water at 0°C, the ice cube sinks – Why?
Answer:

• In an ice cube, each atom is surrounded tetrahedrally by four water molecules through a hydrogen bond and its density is low.
• Liquid water at 0°C has a density of 999.82 kg/cm³. Maximum density is attained by water only at 4°C as 1000 kg/cm³.
• When the temperature changed from 4°C to 0°C, the density of water decreases rather than increases. This is called the anomalous expansion of water.
• The reason for this phenomenon lies in the structure of ice lattice and hydrogen bonding in water.
• At 0°C, the ice cube sinks in liquid water at 0°C because of the lesser density and greater volume of water.

Question 24.
Discuss the three types of Covalent hydrides.
Answer:
Covalent hydrides are the compound in which hydrogen is attached to another element by sharing electrons. The most common examples of covalent hydrides of non-metals are methane, ammonia, water, and hydrogen chloride. Covalent hydrides are further divided into three categories, viz., electron precise (CH₄ C₂H₆), electron-deficient (B₂H₆), and electron-rich hydrides (NH₃H₂ O). Since most of the covalent hydrides consist of discrete, small molecules that have relatively weak intermolecular forces, they are generally gases or volatile liquids.

Question 25.
Predict which of the following hydrides is gas on a solid (a) HCl (b) NaH. Give your reason.
Answer:

• At room temperature, HCl is a colourless gas, and the solution of HCl in water is called hydrochloric acid and it is in a liquid state.
• Sodium hydride NaH is an ionic compound and it is made of sodium cations (Na⁺) and hydride (H^–) anions. It has an octahedral crystal structure. It is an alkali metal hydride.

Question 26.
Write the expected formulas for the hydrides of 4th-period elements. What is the trend in the formulas? In what way the first two numbers of the series different from the others?
Answer:
The expected formulas of the hydrides of 4th-period elements are MH or MH₂. However, except for the first two members, many of the elements form non-stoichiometric interstitial hydrides with variable composition. The first two members of the period alkali metal (Potassium) and alkali earth metal (Calcium) forms ionic hydrides.

Question 27.
Write the chemical equation for the following reactions.

1. the reaction of hydrogen with tungsten (VI) oxide NO₃ on heating.
2. hydrogen gas and chlorine gas.

Answer:

1. 3H₂ + WO₂ → W + 3H₂O
   Hydrogen reduces tungsten (VI) oxide. WO₃ to tungsten at high temperature.
2. H₂ + Cl₂ → 2HCl (Hydrogen Chloride)
   Hydrogen reacts with chlorine at room temperature under light to give hydrogen chloride.

Question 28.
Complete the following chemical reactions and classify them into (a) hydrolysis (b) redox (c) hydration reactions.
(i) KMnO₄ + H₂O₂ →
(ii) CrCl3+ H₄O →
(iii) CaO + H₂O →
Answer:
(i) KMnO₄ + H₂O₂ → 2KMnO₂ + 2KOH + 2H₂O + 3O₂
The reaction of potassium permanganate with hydrogen peroxide is a redox reaction.

(ii) CrCl₃ + H₂O → [Cr(H₂O)₆]Cl₃
It is a hydration reaction. Many salts crystallized from aqueous solutions form hydrated crystals. The water in the hydrated salt may form co-ordinate bonds.

(iii) CaO + H₂O → Ca(OH)₂
It is a hydrolysis reaction. Calcium oxide hydrolyses to calcium hydroxide.

Question 29.
Hydrogen peroxide can function as an oxidizing agent as well as a reducing agent. Substantiate this statement with suitable examples.
Answer:
Hydrogen peroxide can function as an oxidizing agent as well as a reducing agent.

• H₂O₂ acts as an oxidizing agent in an acidic medium. For example,
  
• H₂O₂ acts as a reducing agent in a basic medium. For example,
  >

Question 30.
Do you think that heavy water can be used for drinking purposes?
Answer:

• Heavy water (D₂O) contains a proton and a neutron. This makes deuterium about twice as heavy as protium, but it is not radioactive. So heavy water is not radioactive.
• If you drink heavy water, you don’t need to worry about radiation poisoning. But it is not completely safe to drink, because the biochemical reaction in our cells is affected by the difference in the mass of hydrogen atoms.
• If you drink an appreciable volume of heavy water, you might feel dizzy because of the density difference. It would change the density of the fluid in your inner ear. So it is unlikely to drink heavy water.

Question 31.
What is the water-gas shift reaction?
Answer:
The carbon monoxide of water gas can be converted to carbon dioxide by mixing the gas mixture with more steam at 400°C and passed over a shift converter containing iron/copper catalysts. This reaction is called the water-gas shift reaction.
CO + H₂O → CO₂ + H₂↑

Question 32.
Justify the position of hydrogen in the periodic table?
Answer:
The hydrogen has the electronic configuration of 1s¹ which resembles with ns¹ general valence shell configuration of alkali metals and shows similarity with them as follows:
1. It forms unipositive ion (H⁺) like alkali metals (Na⁺, K⁺, Cs⁺)
2. It forms halides (HX), oxides, (H₂O), peroxides (H₂O₂), and sulphides (H₂S) like alkali metals (NaX, Na₂O, NaH₂OH₂, NaH₂S)
3. It also acts as a reducing agent.

However, unlike alkali metals which have ionization energy ranging from 377 to 520 kJ mol^-1, hydrogen has 1,314 kJ mol^-1 which is much higher than alkali metals.

Like the formation of halides (X^–) from halogens, hydrogen also has a tendency to gain one electron to form a hydride ion (H^–) whose electronic configuration is similar to the noble gas, helium. However, the electron affinity of hydrogen is much less than that of halogen atoms. Hence, the tendency of hydrogen to form hydride ion is low compared to that of halogens to form the halide ions as evident from the following reactions:
\(\frac{1}{2}\) H₂ + e^– → H^–                         ∆H = +36 kcalmol^-1
\(\frac{1}{2}\) Br₂ + e^– → Br^–                       ∆H = -55 kcalmol^-1

Since hydrogen has similarities with alkali metals as well as halogens; it is difficult to find the right position in the periodic table. However, in most of its compounds hydrogen exists in a +1 oxidation state. Therefore, it is reasonable to place the hydrogen in group 1 along with alkali metals as shown in the latest periodic table published by IUPAC.

Question 33.
What are isotopes? Write the names of isotopes of hydrogen.
Answer:

1. Isotopes are atoms of the same element that have the same atomic number but having different mass numbers (or) Isotopes are atoms with the same number of protons and electrons but differ in a number of neutrons.
2. Hydrogen has three naturally occurring isotopes namely Protium (₁H¹), Deuterium (₁H²), and Tritium (₁H³).
   

Question 34.
Give the uses of heavy water.
Answer:
The uses of heavy water are as follows:

1. Heavy water is widely used as a moderator in nuclear reactors as it can lower the energies of fast neutrons
2. It is commonly used as a tracer to study organic reaction mechanisms and mechanism of metabolic reactions
3. It is also used as a coolant in nuclear reactors as it absorbs the heat generated.

Question 35.
Explain the exchange reactions of deuterium.
Answer:
Deuterium can replace reversibly hydrogen in compounds either partially or completely depending upon the reaction conditions. These reactions occur in the presence of deuterium.

Question 36.
How do you convert para-hydrogen into ortho hydrogen?
Answer:
At room temperature, normal hydrogen consists of about 75% ortho-form and 25% para-form. As the ortho-form is more stable than para-form, the conversion of one isomer into the other is a slow process. However, the equilibrium shifts in favour of para hydrogen when the temperature is lowered.

The para-form can be catalytically transformed into an I ortho-form using platinum or iron. Alternatively, it can also be converted by passing an electric j discharge, heating above 800°C, and mixing with paramagnetic molecules such as O₂, NO, NO_2, or with nascent/atomic hydrogen.

Question 37.
Mention the uses of deuterium.
Answer:

• Deuterium is used as a tracer element.
• Deuterium is used to study the movement of groundwater by isotopic effect.

Question 38.
Explain the preparation of hydrogen using electrolysis.
Answer:
High purity hydrogen (> 99.9 %) is obtained by the electrolysis of water containing traces of acid or alkali or the electrolysis of an aqueous solution of sodium hydroxide or potassium hydroxide using a nickel anode and iron cathode. However, this process is not economical for large-scale production.
At anode:
2OH^– → H₂O + \(\frac{1}{2}\)O₂ + 2e^–
At cathode:
2H₂O + 2e^– → 2OH^– + H₂
Overall reaction:
H₂O → H₂ + \(\frac{1}{2}\)O₂

Question 39.
A group metal (A) which is present in common salt reacts with (B) to give compound (C) in which hydrogen is present in a -1 oxidation state. (B) on reaction with a gas (C) to give universal solvent (D). The compound (D) reacts with (A) to give (B), a strong base. Identify A, B, C, D, and E. Explain the reactions.
Answer:
1.Group (1) metal (A) is present in common salt NaCl. So, (A) is sodium – Na.
2. Sodium reacts with hydrogen (B) to give sodium hydride – NaH (C) in which hydrogen is in a -1 oxidation state.

3. Hydrogen on reaction with oxygen (O₂) gas which is (C) to give universal solvent water (D).

4. Water (D) reacts with sodium metal (A) to give a strong base sodium hydroxide NaOH which is (E).

Question 40.
An isotope of hydrogen (A) reacts with a diatomic molecule of the element which occupies group number 16 and period number 2 to give compound (B) is used as a modulator in a nuclear reaction. (A) adds on to a compound (C), which has the molecular formula C₃H₆ to give (D). Identify A, B, C, and D.
Answer:
1. An isotope of hydrogen Deuterium (A) reacts with a diatomic molecule of element belongs to group number 16 and period number 2 oxygen O₂ to give a compound (B) which is heavy water D₂O. D₂O is used as a moderator in a nuclear reaction.

2. Deuterium reacts with C₃H₆ propane (C) to give Deutero propane C₂D₆ (D).

Question 41.
NH₃ has an exceptionally high melting point and boiling point as compared to those of the hydrides of the remaining element of group 15- Explain.
Answer:

1. NH₃ has an exceptionally high melting point and boiling point due to hydrogen bonding between NH₃ molecules.
2. Each molecule can form a maximum of 4 hydrogen bonds but on average 1 hydrogen bond per molecule as there is only one lone pair on NH₃ available for hydrogen bonding.
3. Hydrogen bonding is a strong intermolecular attraction as H on NH₃ acts as a proton due to partial positive on it the whole N has the partial negative charge. Thus when the very polarized H comes close to an N atom in another NH₃ molecule, a very strong hydrogen bond is formed.
4. Due to many strong intermolecular interactions compared to weaker permanent dipole-dipole interactions between other XH₃ molecules in group 15, a large amount of energy are required to overcome the forces, giving it the highest boiling point and highest melting point.

Question 42.
Why interstitial hydrides have a lower density than the parent metal.
Answer:
In interstitial hydrides, hydrogen occupies the interstitial sites. These hydrides show properties similar to parent metals. Most of these hydrides are non-stoichiometric with variable composition. Hence, interstitial hydrides have a lower density than the parent metal.

Question 43.
How do you expect the metallic hydrides to be useful for hydrogen storage?
Answer:
In metallic hydrides, hydrogen is adsorbed as H-atoms. Due to the adsorption of H atoms, the metal lattice expands and becomes unstable. Thus, when metallic hydride is heated, it decomposes to form hydrogen and finely divided metal. The hydrogen evolved can be used as fuel.

Question 44.
Arrange NH₃, H₂O, and HF in the order of increasing magnitude of hydrogen bonding and explain the basis for your arrangement.
Answer:
When a hydrogen atom is covalently bonded to a highly electronegative atom such as nitrogen, the bond is polarized. Due to this effect, the polarized hydrogen atom is able to form a weak electrostatic interaction with another electronegative atom present in the vicinity. This interaction is called hydrogen bonding. The magnitude of hydrogen bonding increases with the increase in the electronegativity of the atom. Hence, the increasing magnitude of hydrogen bonding of NH₃, H₂O, and HF follows the order NH₃ < H₂O < HF.

Question 45.
Compare the structures of H₂O and H₂O₂.
Answer:
In water, O is sp³ hybridized. Due to stronger lone pair-lone pair repulsions than bond pair-bond pair repulsions, the HOH bond angle decreases from 109.5° to 104.5°. Thus water molecule has a bent structure.

H₂O₂ has a non-planar structure. The 0 – H bonds are in different planes. Thus, the structure of H₂O₂ is like an open book.

Samacheer Kalvi 11th Chemistry Hydrogen Additional Questions Solved

I. Choose the correct answer:

Question 1.
The simplest atom which contains one electron and one proton is
(a) Helium
(b) Deuterium
(c) Hydrogen
(d) Tritium
Answer:
(c) Hydrogen

Question 2.
is the most abundant 90% of all atoms…………
(a) Lithium
(b) Hydrogen
(c) Oxygen
(d) Silicon
Answer:
(A) Hydrogen

Question 3.
Which of the following properties of hydrogen similar to alkali metals?
1. It forms a uni negative ion.
2. It forms halides, oxides, and sulphides similar to alkali metals.
3. It also acts as a reducing agent.
(a) 1 and 2
(b) 2 and 3
(c) 1 and 3
(d) 1, 2 and 3
Answer:
(b) 2 and 3

Question 4.
Which one of the metal is used to convert para-hydrogen into ortho hydrogen?
(a) Copper
(b) Aluminium
(c) Sodium
(d) Platinum
Answer:
(d) Platinum

Question 5.
Hydrogen is placed in the ________ of the periodic table.
(a) group – 1
(b) group – 17
(c) group – 18
(d) group – 2
Answer:
(a) group – 1

Question 6.
Which of the following is not used in the conversion of para hydrogen into ortho hydrogen?
(a) by heating more than 800°C
(b) bypassing an electric discharge
(c) by mixing with atomic hydrogen
(d) by mixing with diamagnetic molecules
Answer:
(d) by mixing with diamagnetic molecules

Question 7.
The radioactive isotope of hydrogen is
(a) protium
(b) deuterium
(c) tritium
(d) heavy hydrogen
Answer:
(c) tritium

Question 8.
Which one of the following does not contain neutron?
(a) ordinary hydrogen
(b) Heavy hydrogen
(c) Radioactive hydrogen
(d) Deuterium
Answer:
(a) ordinary hydrogen

Question 9.
The half-life period of tritium is ______(in years).
(a) 13.2
(b) 10.5
(c) 12.3
(d) 15.8
Answer:
(c) 12.3

Question 10.
Which of the following is used in illumination of wristwatches?
(a) Phosphorous
(b) Radon
(c) Tritium
(d) Deuterium
Answer:
(c) Tritium

Question 11.
The percentage of ortho and para forms of normal hydrogen at room temperature is
(a) 25% and 75%
(b) 40% and 60%
(c) 60% and 40%
(d) 75% and 25%
Answer:
(d) 75% and 25%

Question 12.
By which rays nuclear reactions are induced in upper atmosphere to produce tritium?
(a) α-rays
(b) β-rays
(c) γ-rays
(d) cosmic rays
Answer:
(d) cosmic rays

Question 13.
The composition of syngas is
(a) CO + N₂
(b) CO + H₂O
(c) CO + H₂
(d) CO₂ + H₂
Answer:
(c) CO + H₂

Question 14.
Consider the following statements ……………..
(i) Tritium is a beta-emitting radioactive isotope of hydrogen.
(ii) Deuterium is known as heavy hydrogen.
(iii) Deuterium is used in emergency exit signs.
Which of the following statement is/are not correct?
(a) (i) only
(b) (iii) only
(c) (i) and (ii)
(d) (i) (ii) and (iii)
Answer:
(b) (iii) only

Question 15.
The conversion of carbon monoxide of the water gas into carbon dioxide is called water gas _______ reaction.
(a) displacement
(b) decomposition
(c) shift
(d) conversion
Answer:
(c) shift

Question 16.
Consider the following statements.
(i)Hydrogen is a colourless, odourless, tasteless heavy and highly inflammable gas.
(ii) Hydrogen is a good reducing agent.
(ii) Hydrogen can be liquefied under low pressure and high temperature.
Which of the above statements is/are not correct?
(a) (i) only
(b) (ii) only (c)
(c) (i) and (iii)
(d) (ii) and (Hi)
Answer:
(c) (i) and (iii)

Question 17.
The CO₂ formed in the water gas shift reaction is absorbed in a solution of
(a) Potassium bicarbonate
(b) Sodium chloride
(c) Potassium sulphate
(d) Potassium carbonate
Answer:
(d) Potassium carbonate

Question 18.
Which one of the following is manufactured in Haber’s process?
(a) SO₃
(b) NH₃
(C) N₂
(d) H₂
Answer:
(b) NH₃

Question 19.
When water is completely electrolyzed, the gas liberated is/are
(a) H₂
(b) D₂
(c) H₂ and D₂
(d) H₂ and T₂
Answer:
(c) H₂ and D₂

Question 20.
Match the List-I and List-II using the correct code given below the list.
List-I
A. Hydrogenation of unsaturated vegetable oils
B. Calcium hydride
C. Liquid hydrogen
D. Atomic hydrogen

List-II
1. Rocket fuel
2. Welding of metals
3. Desiccant
4. Margarine

Answer:

Question 21.
Statement-I: Hydrogen is placed at the top of the group which is in-line with the latest periodic table.
Statement-II: Hydrogen has a tendency to lose its electron to form H⁺, thus showing electropositive character like alkali metals. On the other hand, hydrogen has a tendency to gain an electron to yield H, thus showing electronegative character like halogens.
(a) Statements-I and II are correct and Statement-II is the correct explanation of statement-I.
(b) Statements-I and II are correct but Statement-II is not the correct explanation of statement-I.
(c) Statement-I is correct but Statement-II is wrong.
(d) Statement-I is wrong but Statement-II is correct.
Answer:
(a) Statements-I and II are correct and Statement-II is the correct explanation of statement-I.

Question 22.
Statement-I: The magnetic moment of para-hydrogen is zero.
Statement-II: The spins of two hydrogen atoms in para H₂ molecule neutralise each other.
(a) Statements-I and II are correct and Statement-II is the correct explanation of statement-I.
(b) Statements-I and II are correct but Statement-II is not the correct explanation of statement-I.
(c) Statement-I is correct but Statement-II is wrong.
(d) Statement-I is wrong but Statement-II is correct.
Answer:
(a) Statements-I and II are correct and Statement-II is the correct explanation of statement-I.

Question 23.
Statement – I: Tritium is a β-emitter.
Statement – II: Radioactive decay of tritium gives \({ }_{2}^{3} \mathrm{He}\) and \({ }_{1}^{0} e\).
The correct statement/s is/are
(a) I alone
(b) II alone
(c) both I and II
(d) both are incorrect.
Answer:
(c) both I and II

Question 24.
Which of the following is used as desiccants to remove moisture from organic solvents?
(a) Calcium hydride
(b) LiAlH₄
(c) Sodium boro hydride
(d) Sodium hydride
Answer:
(a) Calcium hydride

Question 25.
Chlorine reacts with water and forms _____ and _____ respectively.
(a) HCl and HOCl
(b) H₂ and HCl
(c) HOCl and H₂
(d) HCl and ClO₂
Answer:
(c) HOCl and H₂

Question 26.
Liquid hydrogen is used as
(a) a rocket fuel as well as in space research
(b) fuel cells for generating electrical energy
(c) cutting and welding torch
(d) desiccant to remove moisture from organic solvent
Answer:
(a) a rocket fuel as well as in space research

Question 27.
Hydrolysis of P₄O₁₀ gives
(a) HPO₂
(b) H₄P₂O₇
(c) H₃PO₃
(d) H₂PO₄
Answer:
(d) H₂PO₄

Question 28.
At the temperature conditions of the earth (300K) the OPR of H₂O is ……………
(a) 2.5
(b) 3
(c) 1
(d) zero
Answer:
(b) 3

Question 29.
Fluorine reacts with water and liberates
(a) hydrogen
(b) oxygen
(c) Fluorine dioxide
(d) HOF
Answer:
(b) oxygen

Question 30.
Which of the following does not have any effect on water?
(a) Sodium
(b) Iron
(c) Lead
(d) Mercury
Answer:
(d) Mercury

Question 31.
The most common metal ions present in hard water are
(a) Magnesium and Iron
(b) Calcium and Aluminium
(c) Magnesium and Calcium
(d) Manganese and Calcium
Answer:
(c) Magnesium and Calcium

Question 32.
Which of the following non-metal reacts with ordinary water?
(a) Carbon
(b) Sulphur
(c) Chlorine
(d) Phosphorous
Answer:
(c) Chlorine

Question 33.
The permanent hardness of water is due to the presence of soluble salts of _____ and ______ of magnesium and calcium.
(a) carbonates and bicarbonates
(b) chlorides and carbonates
(c) bicarbonates and sulphates
(d) chlorides and sulphates
Answer:
(d) chlorides and sulphates

Question 34.
Which one of the following is used as a bleach?
(a) Cl₂ water
(b) Br, water
(c) Water gas
(d) Liquid hydrogen
Answer:
(a) Cl₂ water

Question 35.
The general formula of zeolites is
(a) NaOAl₂O₃. ^xSiO₂. ^yH₂O
(b) Na₂O.Al₂O₃. ^ySiO₂. ^xH₂O
(c) NaOH.Al₂O₃. ^xSiO₂. ^yH₂O
(d) NaO.Al (OH)₃ .^xSiO₂. ^yH₂O
Answer:
(a) NaOAl₂O₃. ^xSiO₂. ^yH₂O

Question 36.
Permanent hardness of water is removed by
(a) boiling
(b) lime
(c) washing soda
(d) chlorine
Answer:
(c) washing soda

Question 37.
_______ is used as a moderator and coolant in nuclear reactors.
(a) Heavy hydrogen
(b) Ortho hydrogen
(c) Hydrogen peroxide
(d) Heavy water
Answer:
(d) Heavy water

Question 38.
In chelating method of softening of hard water is used.
(a) magnesia
(b) lime
(c) EDTA
(d) washing soda
Answer:
(c) EDTA

Question 39.
The percentage of hydrogen peroxide in ‘100 volume’ is
(a) 40
(b) 30
(c) 50
(d) 20
Answer:
(b) 30

Question 40.
Match the List-I and List-Il using the code given below the list.
List-I
A. Heavy water
B. Hydrogen peroxide
C. Heavy hydrogen
D. Lithium Aluminium hydride

List-Il
1. Antiseptic
2. Moderator
3. Reducing agent
4. Tracer

Answer:

Question 41.
______ present in the glass catalyses the disproportionation reaction of hydrogen peroxide.
(a) Silica
(b) Alkali metals
(c) fluorine
(d) Oxygen
Answer:
(b) Alkali metals

Question 42.
Statement-I: Heavy water has been widely used as moderator in nuclear reactors.
Statement-Il: Heavy water can lower the energies of fast moving neutrons.
(a) Statements-I and II are correct and Statement-Il is the correct explanation of statement-I.
(b) Statements-I and II are correct but Statement-IT is not the correct explanation of statement-I;
(c) Statement-I is correct but Statement-Il is wrong.
(d) Statement-I is wrong but Statement-Il is correct.
Answer:
(a) Statements-I and II are correct and Statement-Ills the correct explanation of statement-I.

Question 43.
Which of the following statement/s are true about hydrogen peroxide?
1. It can act both as an oxidizing agent and a reducing agent.
2. It is used in water treatment to oxidize pollutants.
3. It is used as a mild analgesic.
4. It restores the white colour of the old paintings,
(a) 1, 2 and 3
(b) 1, 3 and 4
(c) 1, 2 and 4
(d) 2, 3 and 4
Answer:
(c) 1, 2 and 4

Question 44.
Which one of the following is an ionic or saline hydride?
(a) SiH₄
(b) GeH₄
(c) B₂H₆
(cl) LiH
Answer:
(d) LiH

Question 45.
The smallest molecule which shows hindered rotation about a single bond is
(a) Hydrogen peroxide
(b) Water
(c) Deuterium oxide
(d) hydrogen
Answer:
(a) Hydrogen peroxide

Question 46.
Which of the following pair is an electron rich hydride?
(a) NH₃, H₂O
(b) CH₄, C₂H₆
(c) B₂H₆, GeH₄
(d) CH₄, SiH₄
Answer:
(a) NH₃, H₂O

Question 47.
Which of the following molecule shows an intramolecular hydrogen bond?
(a) Water
(b) Ammonia
(c) Salicylaldehyde
(d) Para-nitrophenol
Answer:
(c) Salicylaldehyde

Question 48.
Metallic hydrides are otherwise called …………….
(a) Salt hydrides
(b) Saline hydrides
(c) molecular hydrides
(d) Interstitial hydrides
Answer:
(d) Interstitial hydrides

Question 49.
Which one of the following is a covalent hydride?
(a) NH₃
(b) BeH₂
(c) NaH
(d) ZrH₂
Answer:
(a) NH₃

Question 50.
Which one of the following is known as a Hydrogen sponge?
(a) Lithium hydride
(b) Diborane
(c) Palladium hydride
(d) Ammonia
Answer:
(c) Palladium hydride

Question 51.
Which of the following is the correct order of stability of bonds?
(a) Hydrogen bond < CovaLent bond < Vanderwaals bond
(b) Vanderwaals bond < Hydrogen bond <Covalent, bond
(c) Vanderwaals bond > Hydrogen bond > Covalent bond
(d) Covalent bond < Hydrogen bond <Vanderwaals bond
Answer:
(b) Vanderwaals bond < Hydrogen bond <Covalent, bond

Question 52.
Which one of the following does not have intramolecular hydrogen bonding?
(a) water
(b) o-nitrophenol
(c) Salicylaldehyde
(d) Salicylic acid
Answer:
(a) water

Question 53.
Which of the following contains intramolecular hydrogen bonding?
(a) Acetic acid
(b) o-nitrophenol
(c) Hydrogen fluoride
(d) water
Answer:
(b) o-nitrophenol

Question 54.
Consider the following statements.
(i) In ice, each oxygen atom is surrounded by hydrogen atoms tetrahedrally to four water molecules.
(ii) Acetic acid exists as a dimer due to intramolecular hydrogen bonding.
(iii) Strong hydrogen bonds lead to an increase in the melting and boiling points.
Which of the above statements is/are not correct? ,
(a) (ii) only
(b) (i) and (iii)
(c) (i) (ii) and (iii)
(d) (i) only
Answer:
(a) (ii) only

Question 55.
Which one of the following is an example for Clathrate hydrate?
(a) CuSO₄.5H₂O
(b) Na₂CO₃. 10H₂O
(c) CH₄. 20 H₂O
(d) FeSO₃.7H₂O
Answer:
(c) CH₄. 20 H₂O

Question 56.
Which one of the following is not a crystalline hydrate?
(a) CH₄. 20H₂O
(b) Na₂,CO₃. 10H₂O
(c) CuSO₄.5H₂O
(d) FeSO₄.7H₂0
Answer:
(a) CH₄. 20H₂O

Question 57.
Statement-I: Hydrogen can be used as a clean-burning fuel.
Statement-II: Hydrogen on combustion give only water as end product and it is free from pollutants.
(a) Statements-I and II are correct and Statement-lI is the correct explanation of statement-I.
(b) Statements-I and II are correct but Statement-Il is not the correct explanation of statement-I.
(e) Statement-I is correct but Statement-Il is wrong.
(d) Statement-I is wrong but Statement-lI is correct.
Answer:
(a) Statements-I and II are correct and Statement-Il is the correct explanation of statement-I.

Question 58.
Which isotope of hydrogen is radioactive?
(a) Protium
(b) Deuterium
(c) Tritium
(d) H
Answer:
(c) Tritium

Question 59.
Which type of elements form interstitial hydrides ………..
(a) s-block and p-block
(b) p-block only
(c) d-block and f-block
(d) s-block only
Answer:
(c) d-block and f-block

Question 60.
Which of the following is named perhydrol and used as an antiseptic?
(a) D₂O
(b) H₂O₂
(c) NaH
(d) B₂H₆
Answer:
(b) H₂O₂

Question 61.
Which of the following causes temporary hardness of water?
(a) MgCl₂
(b) Na₂SO₄
(c) Mg(HCO₃)₂
(d) NaCl
Answer:
(c) Mg(HCO₃)₂

Question 62.
Which of the following can oxidise Hydrogen peroxide?
(a) acidified KMnO₄
(b) Cu
(c) dil. HNO₄
(d) CrO₂Cl₂
Answer:
(a) acidified KMnO₄

Question 63.
Which type of hydrides are generally non-stoichiometric in nature?
(a) Metallic hydride
(b) Covalent hydrides
(c) Ionic hydride
(d) Saline hydride
Answer:
(a) Metallic hydride

Question 64.
Hydrogen gas is generally prepared by the ………….
(a) reaction of granulated zinc with dilute H₂SO₄
(b) reaction of zinc with cone, H₂SO₄
(c) reaction of pure zinc with dil. H₂SO₄
(d) action of stream on red hot coke
Answer:
(a) reaction of granulated zinc with dilute H₂SO₄

Question 65.
The higher density of water than that of ice is due to ……………
(a) dipole-dipole interaction
(b) dipole-induced dipole interaction
(c) hydrogen bonding
(d) all of these
Answer:
(c) hydrogen bonding

Question 66.
Hydrogen resembles halogens in many respects for which several factors are responsible. Of the following factors which one is most important in this respect?
(a) Its tendency to lose an electron to form a cation.
(b) Its tendency to gain an electron to attain stable electronic configuration.
(c) Its low negative electron gain enthalpy value.
(d) It’s small in size.
Answer:
(b) Its tendency to gain an electron to attain stable electronic configuration.

Question 67.
Metal hydrides are ionic, covalent, or molecular in nature. Among LiH, NaH, KH, RbH, CsH, the correct order of increasing ionic character is ………….
(a) LiH>NaH>CsH>KH>RbH
(b) LiH<NaH<KH<RbHCsH>NaH>Kil>LIH
(d) NaH>CsH>RbH>LiH>KH
Answer:
(b) LiH<NaH<KH<RbH<CsH

Question 68.
Statement-I: Permanent hardness of water is removed by treatment with washing soda ………..
Statement-II: Washing soda reacts with soluble magnesium and calcium sulphate to form insoluble carbonate.
(a) Statements-I and II are correct and Statement-Il is the correct explanation of statement-I.
(b) Statements-I and II are correct but Statement-Il is not the correct explanation of statement-I.
(c) Statement-I is correct but Statement-II is wrong.
(d) Statement-I is wrong but Statement-II is correct.
Answer:
(a) Statements-I and II are correct and Statement-Ills the correct explanation of statement-I.

Question 69.
Which of the following is a saline hydride?
(a) HCl
(b) NH₃
(c) NaH
(d) PbH
Answer:
(e) NaH

Question 70.
Which metal does not liberate H₂ gas from dilute aqueous hydrochloric acid at 298 K?
(a) Mg
(b) Zn
(c) Al
(d) Cu
Answer:
(d) Cu

Question 71.
When zeolite is treated with hard water, the sodium ions are exchanged with …………
(a) H⁺ ions and Cl^– ions
(b) Ca²⁺ ions
(c) Cl^– ions
(d) Ca²⁺ ions and Mg²⁺ ions
Answer:
(d) Ca²⁺ ions and Mg²⁺ ions

Question 72.
The most abundant element in the universe is …………..
(a) Carbon
(b) Nitrogen
(c) Silicon
(d) Hydrogen
Answer:
(d) Hydrogen

Question 73.
Which of the following can effectively remove all types of the hardness of water?
(a) Soap
(b) Slaked lime
(c) Washing soda
(d) Zeolite
Answer:
(a) Soap

Question 74.
A commercial sample of H₂O₂ is labelled as 100 volume. Its percentage strength is nearly
(a) 10%
(b) 30%
(c) 100%
(d) 90%
Answer:
(b) 30%

Question 75.
Which of the following will not produce dihydrogen gas?
(a) Cu + dil (HCl)
(b) CH_2(g) + H₂O_(g)
(c) Zn + dil. HCl
(cl) C_(s) + H₂O_(g)
Answer:
(a) Cu + dil. (HCl)

Samacheer Kalvi 11th Chemistry Hydrogen 2-Mark Questions
Question 1.
Draw and define ortho and para hydrogen molecule.
Answer:
Molecular hydrogen have ortho and para form in which the nuclear spins are aligned or opposed, respectively.

Question 2.
Write the physical properties of Hydrogen?
Answer:
Hydrogen is a colorless, odorless, tasteless, lightest, and highly flammable gas. It is a non-polar diatomic molecule. It can be liquefied under low temperature and high pressure. Hydrogen is a good reducing agent.

Question 3.
Mention the uses of tritium.
Answer:

• Tritium has replaced radium in applications such as emergency exit signs.
• Tritium is used in illumination of wristwatches.

Question 4.
Draw the structures of three isotopes of hydrogen, Hydrogen Deuterium
Answer:

Question 5.
What is the half-life period of tritium? How is it undergoes radioactive disintegration?
Answer:

• The half-life of tritium = 12.33 years.
• Tritium is a beta-emitting radioactive isotope of hydrogen.
  

Question 6.
How will you convert para-hydrogen into ortho hydrogen?
Answer:
The para-form can be catalytically transformed into ortho-form using platinum or iron. Alternatively, it can also be converted by passing an electric discharge, heating above 800°C, and mixing with paramagnetic molecules such as O₂, NO, NO_2, or within ascent/atomic hydrogen.

Question 7.
How ammonia is manufactured from Hydrogen? Give the uses of ammonia.
Answer:

• Ammonia is manufactured by Habe’s prôcess in which the largest consumer of hydrogen is used.
  N_2(g) + 3H_2(g) ⇌ 2 NH_3(g)
• Ammonia is employed for the manufacture of nitric acid, fertilizers, and explosives.

Question 8.

Question 9.
What is hydrogenation? Give one example.
Answer:
Hydrogenation is a reaction in which the addition of hydrogen to an alkene /alkyne. Compounds containing multiple bonds.

Question 10.
What is syngas? Why is it called so?
Answer:
Water gas is also called syngas as it is used in the synthesis of organic compounds such as methanol and simple hydrocarbons.

Question 11.
How alkali metals react with water? Give an equation?
Answer:
The most reactive alkali metals decompose water in the cold with the evolution of hydrogen and leaving an alkali solution.
2Na_(s) +2H₂O_(l) → 2NaOH_(aq) +H_2(g)

Question 12.
How is Tritium prepared?
Answer:
Tritium is present only in trace amounts. So it can be artificially prepared by bombarding lithium with slow neutrons in a nuclear fission reactor. The nuclear transmutation reaction for this process is as follows.
\({ }_{3}^{6} L i\) + \({ }_{0}^{1} n\) → \({ }_{2}^{4} \mathrm{He}\) + \({ }_{1}^{3} T\)

Question 13.
Explain the action of chlorine with water.
Answer:
Chlorine reacts with the water to form hydrochloric acid and hypochlorous acid.
Cl_2(g) + H₂O_(l) → HCl_(aq) + HOCl_(aq)

Question 14.
What is the deuterium exchange reaction?
Answer:
Deuterium can replace reversibly hydrogen in compounds either partially or completely depending upon the reaction conditions. These reactions occur in the presence of deuterium or heavy water.
CH₄ + 2D₂ → CD₄ + 2H₂
2NH₃ + 3D₂ → 2ND₃ + 3H₂

Question 15.
What ¡s permanent hardness of water? How ¡t will be removed?
Answer:
The permanent hardness of water is due to the presence of soluble salts of magnesium and calcium in the form of chlorides and suiphates in water. It can be removed by adding washing soda which reacts with these metal chlorides and suiphates in hard water to form insoluble carbonates.
MCl_2(aq) + Na₂CO_3(aq) → MCO_3(s) + 2NaCl_(aq)
MSO_4(aq) + Ni₂ CO_3(aq) → MCO_3(s) + Na₂SO_4(s)
Where M = Ca or Mg.

Question 16.
Water is an amphoteric oxide. Give reason.
Answer:
Water is an amphoteric oxide. It has the ability to accept as well as donate protons and hence it can act as an acid or a base. For example, in the reaction with HCl, it accepts proton whereas in the reaction with weak base ammonia it donates a proton.
NH₃ + H₂O → NH₄⁺ + OH^–
HCl + H₂O → H₃O⁺ + Cl^–

Question 17.
H₂O₂ is always stored in plastic bottles. Why?
Answer:
The aqueous solution of hydrogen peroxide is spontaneously disproportionate to give oxygen. The reaction is slow but it is explosive when it is catalyzed by metal or alkali dissolved from glass. For this reason, its solution are stored in plastic bottles.
H₂O_2(aq) → H₂O_(l) + ½ O_2(g)

Question 18.
Why H₂O₂ ¡s used as mild antiseptic?
Answer:
The oxidising property of hydrogen peroxide and harmless nature of its products such as water and oxygen, leads to oxidation of pollutants in water and act as a mild antiseptic.

Question 19.
What is the permanent hardness of water?
Answer:
The permanent hardness of water is due to the presence of soluble salts of magnesium and calcium in the form of chlorides and sulphates.

Question 20.
What is meant by 100 – volume hydrogen peroxide?
Answer:
A 30% solution is marketed as 100 – volume hydrogen peroxide indicating that at STP, 100 volumes of oxygen are liberated per millimeter of the solution.

Question 21.
What is heavy water? How is it obtained?
Answer:
Heavy water (D₂O) is the oxide of heavy hydrogen. One part of heavy water is present in 5000 parts of ordinary water. It is mainly obtained as the product of the electrolysis of water.

Question 22.
What is meant by binary hydride? Give example.
Answer:
A binary hydride is a compound formed by hydrogen with other electropositive elements including metals and non-metals, e.g., LiH or MgH₂.

Question 23.
How does hard water produces less foam with detergents?
Answer:
The cleaning capacity of soap is reduced when used in hard water. Soaps are sodium or potassium salts of long chain fatty acids (e.g., coconut oil). When soap is added to hard water, the divalent magnesium and calcium ions present in hard water react with soap. The sodium salts present in soaps are converted to their corresponding magnesium and calcium salts which are precipitated as scum/precipitate.
M²⁺ + 2RCOONa → (RCOO)₂M + 2Na⁺
M = Ca or Mg, R = C₁₇H₃₅

Question 24.
What are the different types of hydrides?
Answer:
The hydrides are classified as Ionic, Covalent and Metallic Hydrides.
Ionic hydride – LiH
Covalent hydride – CH₄
Metallic hydride -TiH

Question 25.
Why metallic hydrides are called interstitial hydrides? Give one example.
Answer:
Metallic hydrides are usually obtained by hydrogenation of metals and alloys in which hydrogen occupies the interstitial sites (voids). Hence, they are called interstitial hydrides. e.g., PdH.

Question 26.
What is hydrogen bonding?
Answer:
When a hydrogen atom (H) is covalently bonded to a highly electronegative atom such as fluorine (F) or oxygen (O) or nitrogen (N), the bond is polarized in such a way that the hydrogen atom is able to form a weak bond between the hydrogen atom of a molecule and the electronegative atom of a second molecule. The bond thus formed is a hydrogen bond and it is denoted by dotted lines (……)

Question 27.
What are the types of hydrogen bonding? Give example.
Answer:
There are two types of hydrogen bonding.

• Intramolecular hydrogen bonding: It can occur with a molecule. e.g., o – nitrophenol.
• Intermolecular hydrogen bonding: It is formed between two molécules of the same type or different type. e.g., H₂O.

Question 28.
Explain the type of bonding present in hydrogen fluoride?
Answer:
In hydrogen fluoride (HF), for example, one molecule is strongly attracted to the fluorine on its neighboring hydrogen. In both liquid and solid, hydrogen fluoride forms long hydrogen-bonded zig-zag chains as a consequence of the orientation of the lone pairs on the fluorine atoms.

Question 29.
Ice is less dense than water at 0°C. Justify this statement.
Answer:
In ice, each oxygen atom is surrounded tetrahedrally by through hydrogen bonds to four water molecules. That is, the presence of two hydrogen atoms and two lone electron pairs (on oxygen) in each water molecule results in a three – dimensional structure. The arrangements creates an open structure, which in turn accounts for the fact that ice is less dense than water at 0°C.

Question 30.
Draw the structure of –

1. Acetic acid
2. Water.

Answer:
1. Acetic acid:

2. Water:

Question 31.
What is a hydrogen bond?
Answer:
When a hydrogen atom (H) is covalently bonded to a highly electronegative atom such as fluorine (F) or oxygen (O) or nitrogen (N), the bond is polarized. Due to this effect, the polarized hydrogen atom is j able to form a weak electrostatic interaction with another electronegative atom present in the vicinity, f This interaction is called a hydrogen bond.

Question 32.
Give the advantages of future Fuel – Hydrogen.
Answer:
Hydrogen is considered as a potential candidate for this purpose as it is a clean-burning fuel. Hence, hydrogen can directly be used as a fuel and can replace existing gasoline (petrol) diesel kerosene-powered engines, and indirectly be used with oxygen in fuel cells to generate electricity. One major advantage of using hydrogen is that the combustion product is essentially free from pollutants; the end-product formed in both cases is water.

Question 33.
What do you understand by the term non-stoichiometric hydrides’? Do you expect this type of hydrides to be formed by alkali metals? Justify your answer.
Answer:
Those hydrides which do not have fixed composition are called non-stoichiometric hydrides, and the composition varies with temperature and pressure. This type of hydrides is formed by d and f-block elements. They cannot be formed by alkali metals because alkali metal hydrides form ionic hydrides.

Question 34.
How does the atomic hydrogen or oxy – hydrogen torch function for cutting and welding purposes? Explain.
Answer:
When hydrogen is burnt in oxygen the reaction is highly exothermic, it produces very high temperature nearly 4000°C which is used for cutting and welding purposes.

Question 35.
How does H₂O₂ behave as bleaching agent?
Answer:
Bleaching action of H₂O₂ is due to the oxidation of colouring matter by nascent oxygen.
H₂ O₂ → H₂O_(l) + O_(g)

Question 36.
Write the properties of hydrogen similar to alkali metals.
Answer:
The hydrogen has the electronic configuration of 1s¹ which resembles with ns¹ general valence shell configuration of alkali metals and shows similarity with them as follows:

• It forms unipositive ion (H⁺) like alkali metals (Na⁺, K⁺, Cs⁺)
• It forms halides (HX), oxides (H₂O), peroxides (H₂O₂), and sulphides (H₂S) like alkali metals (NaX, Na₂O, Na₂O₂, Na₂S)
• It also acts as a reducing agent.

Question 37.
Write the chemical properties of deuterium.
Answer:
Like hydrogen, deuterium also reacts with oxygen to form deuterium oxide called heavy water. It also reacts with halogen to give corresponding halides.
2D₂ + O₂ → 2D₂O
D₂ + X₂ → 2DX (X = F, Cl, Br & I)

Deuterium can replace reversibly hydrogen in compounds either partially or completely depending upon the reaction conditions. These reactions occur in the presence of deuterium or heavy water
CH₄ + 2D₂ → CD₄ + 2H₂
2NH₃ + 3D₂ → 2ND₃ + 3H₂

Question 38.
Why is hydrogen peroxide stored ¡n wax-lined plastic coloured bottles?
Answer:
The decomposition of H₂O₂ occurs readily in the presence of rough surface (acting as catalyst). It is also decomposed by exposure of light. Therefore, wax-lined smooth surface and coloured bottles retard the decomposition of H₂O₂.

Samacheer Kalvi 11th Chemistry Hydrogen 3 – Mark Questions

Question 1.
Compare the properties of ortho and para hydrogen.
Answer:

s.no	Properties	Ortho hydrogen	Para hydrogen
1.	Melting point	13.95 K	13.83 K
2.	Boiling point	20.39 K	20.26 K
3.	Vapour pressurec	Normal	higher
4.	Magnetic moment	Twice	zero

Question 2.
Compare the properties of isotopes of hydrogen.
Answer:

s.no	Property	Protium	Deuterium	Tritium
1.	Atomic nature	H	D	T
2.	Atomic mass	1.008	2.014	3.016
3.	Nuclear stability	Stable	Stable	Radioactive
4.	Molecular hydrogen	H2	D2	T2
5.	Abundance(%)	99.985	0.015	᷉10-16
6.	Molecular mass	2.016	4.028	6.032

Question 3.
Draw the structure of the isotopes of hydrogen and distinguish them.
Answer:

Question 4.
Explain the different methods of preparation of Tritium with the equation.
Answer:
It occurs naturally as a result of nuclear reactions induced by cosmic rays in the upper atmosphere.

Question 5.
How would you prepare hydrogen in the laboratory?
Answer:
Small amounts of hydrogen are conveniently prepared in laboratory by the reaction of metals, such as zinc, iron and tin, with dilute acid.
Zn_(s)  + 2HCl_(aq) → ZnCl_2(s) + H_2(g)
In principle, any metal with a negative standard reduction potential will react with an acid to generate hydrogen.

Question 6.
What happens when hydrogen reacts with –

1. O₂
2. Cl₂
3. Na ?

Answer:

1. 2 H_2(g) + O_2(g) → 2 H₂O_(l) – Water
2. H_2(g) + Cl_2(g) → 2 HCl_(g) – Hydrogen Chloride
3. 2 Na_(s) + H_2(g) → 2 NaH_(s) – Sodium hydride

Question 7.
Write a note about ortho water and para water.
Answer:

1. Water exists in space in the interstellar clouds, ¡n proto-planetary disks, in the comets and icy satellites of the solar system, and on the Earth.
2. In particular, the ortho-to-para ratio (OPR) of water in space has recently received attention. Like hydrogen, water can also be classified into ortho-H₂O and para-H₂O, in which the directions are antiparallel.
   
3. At the temperature conditions of the Earth (300 K), the OPR of H₂O is 3.
4. At low temperatures below (< 50 K) the amount of para-H₂O increases. It is known that the OPR of water in interstellar clouds and comets has more para-H₂O (OPR = 2.5) than on Earth.

Question 8.
Water ¡s an amphoteric oxide. Justify this statement.
Answer:

1. Water is an amphoteric oxide. It has the ability to act an acid as well as a base. That is, water shows this behavior when it reacts with hydrogen chloride and ammonia.
2. When water reacts with ammonia, it behaves as an acid.
   
3. When water reacts with hydrogen chloride, behaves as a base.
   
   So water is an amphoteric oxide.

Question 9.
How is the temporary hardness of water removed by boiling?
Answer:
Temporary hardness is primarily due to the presence of soluble bicarbonates of magnesium and calcium. This can be removed by boiling the hard water followed by filtration. Upon boiling, these salts decompose into insoluble carbonate which leads to their precipitation. The magnesium carbonate thus formed further hydrosol used to give insoluble magnesium hydroxide.
Ca(HCO₃)₂ → CaCO₃ + H₂O + CO₂Mg(HCO₃) → MgCO₃ + H₂O
CO₂MgCO₃ + H₂O → Mg(OH)₂ + CO₂
The resulting precipitates can be removed by filtration.

Question 10.
Explain the action of soap with hard water.
Answer:

• The cleaning capacity of soap is reduced when used in hard water.
• Soaps are sodium or potassium salts of long-chain fatty acids.
• When soap is added to hard water, the divalent magnesium and calcium cations present in hard water react with soap.
• The sodium salts present in soaps are converted to their corresponding magnesium and calcium salts which are precipitated as scum or precipitate.
  M²⁺ + 2RCOONa (RCOO)₂M_(s) + 2Na⁺_(aq);
  Where, M Ca or Mg;
  R = C₁₇H₃₅.

Question 11.
Write the chemical properties of heavy water.
Answer:
When compounds containing hydrogen are treated with D₂O, hydrogen undergoes an exchange for deuterium 2NaOH + D₂O → 2NaOD + HOD
HCl + D₂O → DCl + HOD
NH₄Cl + 4D₂O → ND₄Cl + 4HOD

These exchange reactions are useful in determining the number of ionic hydrogens present in a given compound. For example, when D₂O is treated with hypo-phosphorus acid only one hydrogen atom is exchanged with deuterium. It indicates that it is a monobasic acid.
H₃PO₂ + D₂O → H₂DPO₂ + HDO
It is also used to prepare some deuterium compounds:
Al₄C₃ + 12D₂O → 4Al(OD)₃ + 3CD₄
CaC₂ + 2D₂O → Ca(OD)₂ + C₂D₂
MgN₂ + 6D₂O → 3Mg(OD)₂ + 2ND₃
Ca₃P₂ + 6D₂O → 3Ca(OD)₂ + 2PD₃

Question 12.
Explain the exchange reactions of deuterium oxide.
Answer:
When compounds containing hydrogen are treated with D₂O, hydrogen undergoes an exchange for Deuterium.

Question 13.
Complete the following reactions.
A1₄C₃ + D₂O → ?
CaC₂ + D₂O →?
Mg₃N₂ + D₂O →?
Ca₃P₂ + D₂O →?
Answer:

Question 14.
What are the uses of hydrogen peroxide?
Answer:

• H₂O₂ is used in water treatment to oxidize pollutants.
• H₂O₂ is used as a mild antiseptic.
• H₂O₂ is used as a bleach in textile, paper and hair-care industry.

Question 15.
Prove that H₂O₂ act as reducing agent ¡n alkaline medium.
Answer:
In alkaline conditions, H₂O₂ act as a reducing agent.
2KMnO_4(aq)(Potassium permanganate) + 3 H₂SO_4(aq) + 5H₂O_2(aq) → K₂ SO₄ + 2MnSO₄ + 8H₂ O_(l) + 5O_2(g)

Question 16.
Write a note about saline (or) ionic hydride.
Answer:
Ionic hydrides composed of an electropositive metal, generally, an alkali or alkaline-earth metal (except beryllium and magnesium) formed by transferring of electrons from metal to hydrogen atoms. They can be prepared by the reaction of elements at about 400°C. These are salt-like, high-melting, white, crystalline solids having hydride ions (H^–) and metal cations (Mⁿ⁺).
2Li_(s) + H_2(g) → 2LiH_(s) (Lithiuinhydride)
2 Ca_(s) + H_2(g) → 2 CaH_2(s) (Calcium hydride)

Question 17.
Write the uses of hydrogen peroxide.
Answer:
The oxidizing ability of hydrogen peroxide and the harmless nature of its products, i.e., water and oxygen, lead to its many applications. It is used in water treatment to oxidize pollutants, as a mild antiseptic, and as bleach in the textile, paper and hair – care industry.

Hydrogen peroxide is used to restore the white colour of the old paintings which was lost due to the reaction of hydrogen sulphide in the air with the white pigment Pb₃(OH)₂ (CO₃)₂ to form black colored lead sulphide. Hydrogen peroxide oxidises black coloured lead sulphide to white coloured lead sulphate, thereby restoring the colour.
PbS + 4H₂O₂ → PbSO₄ + 4H₂O

Question 18.
What is intramolecular hydrogen bonding? Explain with an example.
Answer:

1. Intramolecular hydrogen bonds are those which occur within one single molecule. This occurs between two functional groups within a molecule.
   
2. An intramolecular hydrogen bond (dashed lines) joins the OH group to the doubly bonded oxygen atom of the carboxyl group on the same molecule. e.g., Salicylic acid.
   
3. Salicylic acid act as an analgesic and antipyretic.

Question 19.
What are intermolecular hydrogen bonds? Explain with example.
Answer:

1. Intermolecular hydrogen bonds occur between two separate molecules. They can occur between any numbers of like or unlike molecules as long as hydrogen donors and acceptors are present in positions in which they can interact.
2. For e.g., Intermolecular hydrogen bonds can occur between ammonia molecules alone, between water molecules alone or between ammonia and water.
   
   

Question 20.
Explain about the importance of hydrogen bonding ¡n proteins.
Answer:

• Hydrogen bonds occur in complex biomolecules such as proteins and in biological systems.
• For example, hydrogen bonds play an important role in the structure of deoxyribonucleic acid (DNA), since it holds together the two helical nucleic acid chains.
• In these systems, hydrogen bonds are formed between specific pairs, for example. with a thymine unit in one chain bonding to an adenine unit in another; similarly, a cytosine unit in one chain bonds to a guanine unit in another.
• Intramolecular hydrogen bonding also plays an important role in the structure of polymers, both synthetic and natural.

Question 21.
What are Clatharate hydrate? Explain it with suitable example.
Answer:

• Gas hydrates ¡n which the guest molecules are not bonded chemically but retained by the structure of host is called Clatharates.
• Water forms clatharate hydrates, e.g., methane hydrate (CH₄ 20H₂O) which arc a type of ice that will bum when a lit match is held to it.
• The structure of methane hydrate is made of linked polyhedra that contains 20 hydrogen-bonded water molecules forming a cage in which methane molecule is trapped.
• Deposits of methane clatharates occur naturally in deep sea bed.
• Hydrates are commonly obtained when water is frozen in presence of a gas such as argon, methane, etc.
• Most gases form hydrates under high pressure.

Question 22.
What are crystalline hydrates? Explain it with example.
Answer:

1. In these, hydrogen bonding is very important. Often the water molecules serve to fill in the interstices and bind together structure.
2. A specific example is CuSO₄  5H₂O.
3. Although there are five water molecules for every divalent copper ion, only four are coordinated to the cation, it’s six-coordination being completed from sulphate anions. The fifth water molecule is held in place of hydrogen bonds, O – H – O, between it and two coordinated water molecules and then coordinate sulphate anion.
4. Water forms hydrated salts during crystallization. Examples, Na₂ CO₃ . 10H₂O, FeSO₄ .7H₂O.
5. The water present in the hydrates is called as water of hydration.

Question 23.
Write the chemical properties and uses of heavy water.
Answer:
When compounds containing hydrogen are treated with D₂O, hydrogen undergoes an exchange for deuterium 2NaOH + D₂O → 2NaOD + HOD
HCl + D₂O → DCl + HOD
NH₄Cl + 4D₂O → ND₄Cl + 4HOD

These exchange reactions are useful in determining the number of ionic hydrogens present in a given compound. For example, when D₂O is treated with hypo-phosphoric acid only one hydrogen atom is exchanged with deuterium. It indicates that it is a monobasic acid.
H₃PO₂ +D₂O → H₂DPO₂ + HDO

It is also used to prepare some deuterium compounds:
Al₄Cl₃ + 12D₂O → 4Al(OD)₃ + 3CD₄
CaC₂ + 2D₂O → Ca(OD)₂ + C₂D₂
Mg₃N₂ + 6D₂O → 3Mg(OD)₂ + 2ND₃
Ca₃P₂ + 6D₂O → 3Ca(OD)₂ + 2PD₃

Uses of Heavy Water:

1. Heavy water is widely used as a moderator in nuclear reactors as it can lower the energies of fast neutrons
2. It is commonly used as a tracer to study organic reaction mechanisms and mechanism of metabolic reactions
3. It is also used as a coolant in nuclear reactors as it absorbs the heat generated.

Question 24.
What causes the temporary and permanent hardness of water?
Answer:
Temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium in water i.e., Ca(HCO₃)₂ and Mg(HCO₃) in water. The permanent hardness of water is due to the presence of soluble chlorides and sulphates of calcium and magnesium i.e., CaCl₂, CaSO₄, MgCl_2, and MgSO₄.

Question 25.
Write chemical reaction to show the amphoteric nature of water.
Answer:
Water is amphoteric in nature because it acts as an acid.

Question 26.
What is the difference between the terms ‘hydrolysis’ and ‘hydration’?
Answer:
Hydrolysis is a chemical reaction in which a substance reacts with water under neutral, acidic or alkaline conditions.

Hydration on the other hand is the property of a chemical compound to take up molecules of water of crystallization and get hydrated.

Samacheer Kalvi 11th Chemistry Hydrogen 5-Mark Questions

Question 1.
Explain about the different industrial preparation of hydrogen.
Answer:
In the large scale, hydrogen is produced currently by steam reforming of hydrocarbons. Steam and methane reacts with each other in the presence of nickel catalyst at 35 atm and at a temperature of 800°C gives hydrogen.
CH_4(g) + H₂O_(g) → CO_(g) +3H_2(g)
Steam is passed over a red hot coke to produce carbon monoxide and hydrogen.

Water is reduced to hydrogen with carbon monoxide by passing over iron oxide catalyst at 400°C.
CO_(g) + H₂O_(g) → CO_2(g) + H_2(g)
Hydrogen is produced as a by-product in oil refining industry during the cracking of long chain hydrocarbons.
C₆H_12(g) → CH_66(g) + 3H_2(g)
Hydrogen is also obtained in the manufacture of chlonne and sodium hydroxide via electrolysis of a concentrated solution of sodium chloride.

Question 2.
What are hydrides? How are they classified?
Answer:
Hydrogen forms binary hydrides with many electropositive elements including metals and non-metals. It also forms ternary hydrides with two metals. E.g., LiBH₄ and LiAlH₄. The hydrides are classified as ionic, covalent, and metallic hydrides according to the nature of bonding.

Hydrides formed with elements having lower electronegativity than hydrogen are often ionic, whereas with elements having higher electronegativity than hydrogen form covalent hydrides.

Ionic (Saline) hydrides:
These are hydrides composed of an electropositive metal, generally, an alkali or alkaline-earth metal, except beryllium and magnesium, formed by the transfer of electrons from the metal to hydrogen atoms. They can be prepared by the reaction of elements at about 400° These are salt-like, high-melting, white crystalline solids having hydride ions (H) and metal cations (Mn+).
2 Li + H₂ → 2LiH

Covalent (Molecular) hydrides:
They are compounds in which hydrogen is attached to another element by sharing of electrons. The most common examples of covalent hydrides of non-metals are methane, ammonia, water and hydrogen chloride. Covalent hydrides are further divided into three categories, viz., electron precise (CH₄, C₂H₆, SiH₄, GeH₄), electron-deficient(B₂H₆) and electron-rich hydrides (NH₃, H₂O). Since most of the covalent hydrides consist of discrete, small molecules that have relatively weak intermolecular forces, they are generally gases or volatile liquids.

Metallic (Interstitial) hydrides:
Metallic hydrides are usually obtained by hydrogenation of metals and alloys in which hydrogen occupies the interstitial sites (voids). Hence, they are called interstitial hydrides; the hydrides show properties similar to parent metals and hence they are also known as metallic hydrides.

Most of the hydrides are non-stoichiometric with variable composition (TiH_{1.5 – 1.8} and PdH_{0.6 – 0.8}), some are relatively light, inexpensive and thermally unstable which make them useful for hydrogen storage applications. Electropositive metals and some other metals form hydrides with the stoichiometry MH or sometimes MH₂ (M = Ti, Zr, Hf, V, Zn).

Question 3.
Describe the process of water softening and purification.
Answer:

1. An idealised image of water softening process involves replacement of cations such as Mg, Ca and Fe in water with sodium ions.by a cation exchange zeolite. The ion exchange zeolites or resins are used to replace the Mg and Ca ions found in hard water with sodium ions.
2. They can be recharged by washing it with a solution containing a high concentration of sodium ions.
3. The calcium and magnesium ions migrate from the zeolite or resin being replaced by sodium ions from the solution until a new equilibrium is reached. That is, the salt is used to recharge an ion exchange medium, which itself is used to soften the water.
4. A couple of other methods, namely chelating method, and reverse osmosis are also used to soften hard water. The chelating method employs a polydentate ligand such as EDTA, while reserve osmosis uses high pressure to force the water through a semi-permeable membrane.
5. In the case of water purification application, ion-exchange zeolites or resins are used to remove toxic (eg., copper) and heavy metal (e.g., cadmium or lead) ions from solution, replacing them with harmless sodium or potassium ions.

Question 4.
(a) How is H₂O₂ prepared?
(b) Explain about the structure of H₂O₂.
Answer:
(a) Hydrogen peroxide can be made by adding a metal peroxide to dilute acid.
BaO_2(s) + H_(s)SO₄ → BaSO_4(s) + H₂O_2(aq)
(b) Structure of H₂O₂

1. H₂O₂ has a non-polar structure. The molecular dimensions in the gas phase and solid phase differ as shown in the figure.

2. Both in gas phase and solid phase, the H₂O₂ molecule adopt a skew configuration due to repulsive interaction of the – OH bonds with lone pairs of electrons on each oxygen atom.

3. Indeed, it is the smallest molecule known to show hindrance rotation about a single bond. in solid phase, the dihedral angle is sensitive and hydrogen bonding decreasing from 111.50 in the gas phase to 90.2°, in the solid phase.

4. Structurally, H₂O₂ is represented by the dihydroxyl formula in which the two O-H groups do not lie in the same plane. In the solid phase of molecule, the dihedral angle reduces to 90.2° due to hydrogen bonding and the O-O-H angle expands from 94.8° to 101.9°.

5. One way of explaining the shape of hydrogen peroxide is that the hydrogen atoms would lie on the pages of a partly opened book, and the oxygen atoms along the spin.

Question 5.
Explain about Hydrogen sponge.
Answer:
1. Hydrogen sponge (or) Metal hydride e.g., the palladium-hydrogen system is a binary hydride (PdH).

2. Upon heating, H atoms diffuse through the metal to the surface and recombine to form molecular hydrogen. Since no other gas behaves this way with palladium, this process has been used to separate hydrogen gas from other gases:
2Pd_(s) + H_2(g) ⇌ 2PdH_(s)

3. The hydrogen molecule readily adsorbs on the palladium surface, where it dissociates into atomic hydrogen. The dissociated atoms dissolve into the interstices or voids (octahedral or tetrahedral) of the crystal lattice.

4. Technically, the formation of metal hydride is by chemical reaction but it behaves like a physical storage method, i.e., it is absorbed and released like a water sponge. Such a reversible uptake of hydrogen in metals and alloys is also attractive for hydrogen Storage and for rechargeable metal hydride battery applications.

Question 6.
How are reducing agents in synthetic organic chemistry prepared?
Answer:
Hydrogen has a tendency to react with reactive metals like lithium, sodium to give corresponding hydrides.
2Li+H₂ → 2LiH
2Na+H₂ → 2NaH
These hydrides are used as reducing agents in synthetic organic chemistry. It is also used to prepare important hydrides such as lithium aluminium hydride and sodium borohydride (organic reducing agents).
4 LiH + AlCl₃ → Li[AIH₄] + 3 LiCl
4 NaH + B(OCH₃)₃ → Na[BH₄] + 3 CH₃ONa

Question 7.
How does water react with –
1. SiCl₄
2. P₄O₁₀
Answer:
1. Water reacts with SiCl₄ to give silica.
SiCl₄ + 4H₂O → Si(OH)₄ + 4HCl

2. Water reacts with P₄O₁₀ to give orthophosphoric acid.

Question 8.
Explain the structure of CuSO₄.5H₂O
Answer:
Copper sulphate pentahydrate CuSO₄.5H₂O. In this compound, 4 water molecules form coordinate bonds while the fifth water molecule present outside the coordination can form an intermolecular hydrogen bond with another molecule as [Cu(H₂O)₂] SO₂.H₂O.

Question 9.
How is hydrogen peroxide prepared on industrial scale?
Answer:
On an industrial scale, hydrogen peroxide is prepared by auto oxidation of of 2-alkyl antliraquinol.

Question 10.
How is hydrogen peroxide is used to restore the white colour of old paintings.
Answer:
Hydrogen peroxide is used to restore the white colour which was lost due to the reaction of hydrogen suiphide in air with the white pigment Pb₃(OH)₂(CO₃)₂ to form black colored lead sulphide (PbS) Hydrogen peroxide oxidises black coloured lead sulphide to white coloured lead sulphate, thereby restoring the colour.
PbS + 4H₂O₂ → PbSO₂ + 4H₂O