AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Students get through AP Inter 1st Year Chemistry Important Questions 8th Lesson Hydrogen and its Compounds which are most likely to be asked in the exam.

AP Inter 1st Year Chemistry Important Questions 8th Lesson Hydrogen and its Compounds

Very Short Answer Questions

Question 1.
The three isotopes of hydrogen differ in their rates of reaction. Give the reasons.
Answer:
Due to variation in enthalpies of bond dissociation of H2, D2, T2 molecules, they differ in their rates of reaction.
The reactivity order: H2 > D2 > T2

Question 2.
Why is dihydrogen used in welding of high-melting metals?
Answer:
Atomic hydrogen and oxy-hydrogen torches generate very high temperatures of 4000K. At such high temperatures only, metals like platinum and quartz having high melting points will melt. So dihydrogen is used in the welding of high melting metals.

Question 3.
Describe One method of producing high purity hydrogen.
Answer:
High purity (> 99.95%) dihydrogen is obtained by electrolysing warm aqueous barium hydroxide solution between nickel electrodes.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 1

Question 4.
Explain the term’SYNGAS’?
Answer:
The mixture of CO and H2 is usually Called as Water gas. It is also called as SYNGAS, because, it is used in the synthesis of “methanol” and some other hydrocarbons.

Question 5.
What is meant by coal gasification? Explain with relevant, balanced equation. [TS19]
Answer:
The process of producing ‘syngas’ from coal is called ‘coal gasification’.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 2

Question 6.
Define the term hydride. How many categories of hydrides are known? Name them. [AP 22]
Answer:
Binary compounds of hydrogen formed with other elements are called hydrides.
Three categories of hydrides are known
a) Ionic or salt like hydrides.
b) Covalent or molecular hydrides.
c) Metallic hydrides.

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 7.
The unusual property of water in condensed phase leads to its high heat Of vaporization. What is that property?
Answer:
The unusual property of water in the condensed phase is due to the presence of intermolecular hydrogen bonding between water molecules.

Question 8.
During Photosynthesis water is oxidized to O2. Which element is reduced?
Answer:
The photosynthesis reaction is
6CO2 + 6H2O → C6H12O6 + 6O2

The oxidation number of Carbon in CO2 is +4. But in the Carbohydrate(C6H12O6) the oxidation number of Carbon is 0. Thus the element Carbon is reduced.

Photosynthesis:
CO2 reacts with H2O in the presence of Chlorophyll and Sunlight and releases Carbohydrates in to atmosphere.

Question 9.
What do you understand by ‘auto protolysis’ of water? Give the equation to represent the autoprotolysis of water.
Answer:
Self-ionisation of water is known as auto protolysis of water.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 3

Significance :
From the above reaction, it is clear that water has the ability to act as an acid as well as base. Thus, water behaves as an amphoteric substance.

Question 10.
Water behaves as an amphoteric substance in the Bronsted sense. How do you explain.
Answer:
Water has ability to act as an acid (proton donor) and a base(proton acceptor). So water behaves as an amphoteric substance in the Bronsted sense.
Ex 1: H2O + HCl ⇌ H3O+ + Cl

In this reaction, H2O accepts one proton from HCl. So H2O acts as a base in this reaction.
Ex 2: H2O + NH3 ⇌ NH+4 + OH

In this reaction, H2O donates one proton to NH3. So H2O acts as an acid in this reaction.

Short Answer Questions

Question 1.
The boiling points of NH3, H2O and HF are higher than those of hydrides of the subsequent members of the group. Give your reasons.
Due to the presence of hydrogen bonds, the boiling points of NH3, H2O and HF are higher than those of hydrides of the subsequent members of the group.

Reasons for forming hydrogen bonds :
High Electronegativity differences between H and N, O, F in their hydrides.

But, the electronegativities of the subsequent members of N, O, F groups are less. So their hydrides are less polar and cannot form hydrogen bonds. Hence the boiling points of the hydrides of the subsequent members of the N,O,F groups have low boiling points.

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 2.
Discuss the position of hydrogen in the periodic table on the basis of its electronic configuration. [AP 20]
Answer:
Electronic configuration of H is 1s¹ This configuration is responsible for its dual nature. It behaves like both Alkali metals and Halogens.

Points in support of placing H in IA group:
a) Just like alkali metals, Hydrogen has one electron in its outer shell (1s¹).
b) Just like alkali metals, Hydrogen forms unipositive ion, H+(aq).
c) Just like alkali metals, Hydrogen shows valency 1 in its compounds.

Also, it is quite reasonable to start the periodic table with an element having the least atomic number (Z = 1).

Points in support of placing H in VIIA group: 1
a) Just like Halogens, Hydrogen is a gaseous non-metal.
b) Just like Halogens, Hydrogen forms uninegative ion, H.
c) Just like Halogens (F2, Cl2….), Hydrogen is a diatomic molecule H2.

Also, Hydrogen has a tendency of gaining one electron to attain stable electronic configuration of He.
Even though it resembles in many properties both with alkali and halogens, it differs from them as well. Hence, the position of hydrogen in the periodic table has become a matter of choice. It can be placed along with alkali metals in IA group (or) along with halogens in VIIA group.

Question 3.
How is the electronic configuration of hydrogen suitable for its chemical reactions?
Answer:
Atomic number of Hydrogen is 1. Hence, its electronic configuration is 1s¹. Due to this half filled orbital configuration, Hydrogen takes part in a reaction by
(i) Loss of the only one electron to form H+.
(ii) Gain of one electron to form Hydride H
Ex: Na + H → Na+ + H
(iii) Sharing electrons to form a single covalent bond.

But, Hydrogen is inert at room temperature, due to its high bond dissociation energy.

Question 4.
What happens when dihydrogen reacts with (a) Chlorine and (b) Sodium metal. Explain
Answer:
(a) Reaction of dihydrogen with chlorine:
Hydrogen reacts with chlorine and forms hydrogen chloride gas.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 4

Here, an electron pair is shared between H and Cl leading to the formation of a covalent molecule.

(b)Reaction of dihydrogen with sodium metal:
Hydrogen reacts with highly reactive sodium and forms sodium hydride.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 5

Here, an electron is transferred from Na to H, leading to the formation of ionic compound NaH.

Question 5.
Write a note on heavy water.
Answer:
1) Molecular formula of heavy water is D2O (Deuterium oxide).

2) Preparation:
Heavy water is obtained by the exhaustive electrolysis of water.

3) Physical Properties:
The physical properties like molecular mass, melting point, Boiling point etc., of D20 are more than that of water.

4) Chemical Properties:
(a) Heavy water reacts with calcium carbide and forms Deutero acetylene.
CaC2 + 2D2O → C2D2 + Ca(OD)2

(b) Heavy water reacts with sulphur trioxide and forms Deutero sulphuric acid.
SO3 + D2O → D2SO4

(c) Heavy water reacts with aluminium carbide and forms Deutero methane
Al4C3 + 12D2O → 3CD4 + 4Al(OD)3

5) Uses of D2O:
(a) It is used as a moderator in nuclear reactors to decrease the speed of neutrons.
(b) It is used to study the reaction mechanism in exchange reactions.
(c) It is used for the preparation of deuterium and its compounds.

Question 6.
Name the isotopes of hydrogen. What is the ratio of the masses of these isotopes? [TS 22]
Answer:
Isotopes of hydrogen:
(i) Hydrogen 1¹H
(ii) Deuterium 1²H or 1²D
(iii) Tritium 1³H or 1³T
The ratio of their masses is 1 : 2 : 3

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 7.
What is water-gas shift reaction? How can the production of dihydrogen be increased by this reaction?
Answer:
‘Water gas’ is produced by passing steam, over red hot coke.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 6

To increase the amount of H2. Now water gas is mixed with steam over iron chromate catalyst. This process is called water gas shift reaction.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 7

The CO2 formed is removed by scrubbing with sodium arsenite solution. Thus we get pure H2.

Question 8.
Complete and balance the following reactions:
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 8
Answer:
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 9

Question 9.
What is the nature of the hydrides formed by elements of 13 group?
Answer:

  1. Group 13 elements form covalent hydrides when they react with hydrogen.
  2. Boron forms a number of stable covalent hydrides with a general formula BnHn+4.
    These are called boranes. Ex: B2H6.
  3. Gallium forms a dimeric hydride Ga2H6 (digallane) and indium forms a polymeric hydride (InH3)n
  4. The hydrides of gallium and indium are not very stable.
  5. Boron, aluminium and gallium form complex anionic hydrides such as
    NaBH4 – Sodium borohydride
    Li AlH4 – Lithium aluminium hydride
    LiGaH4 – Lithium gallium hydride
    These are powerful reducing agents.
  6. Thallium does not form any hydride.

Question 10.
Discuss the principle and the method of softening of hard water by synthetic, ion- exchange resins.
Answer:
I) Ion Exchange method:

  1. This method is useful to remove the permanent hardness of water.
  2. It is also named as permutit (or) zeolite process.
  3. Permutit is the artificial zeolite i.e., sodium aluminium orthosilicate (Na2Al2Si2O8. XH2O (or) NaAlSiO4)
  4. Permutit in short form is written as Naz.
  5. When permutit is added to hard water, the following ion-exchange reactions take place.
    2Na(s) + Ca+2(aq) → CaZ2(s) + 2Na+(aq)
    2Na(s) + Mg+2(aq) → MgZ2(s) + 2Na+(aq)
  6. CaZ2 and MgZ2 are called as exhausted permutit. These are regenerated to permutit by the treatment with brine solution (aq NaCl solution).
    CaZ2(s) + 2Na+(aq) → 2NaZ(s) + Ca+2(aq)

II) Synthetic resins method:

  1. Hardwater is softened by using synthetic cation exchangers.
  2. This method is more efficient than zeolite process.
  3. Pure water (de-ionized) is obtained by passing water successively through a Cation exchange resin and an anion exchange resin:
  4. Cation exchange resin contains acidic groups like (RSO3H) or RCOOH. (Here R stands for Resin.)
  5. Anion exchange resin contains basic groups like (RNH3OH)
  6. First hard water is passed through cation exchange resin. Then it absorbs all cations Ca2+ and Mg2+ ions present in the hard water and releases H+ions.
    2RCOOH + Ca2+ → (RCOO)2Ca + 2H+
    2RCOOH + Mg2+ → (RCOO)2Mg + 2H+
  7. Now the water coining from the cation tank is passed through a tank containing anion exchange resin. This resin absorbs all anions like Cl, SO2-4 etc. from the hard water and releases OH ions.
    RNH+3OH +Cl → RNH3Cl + OH
    2RNH+3OH + SO2-4 → (RNH+3)2SO4 + 2OH
  8. The H+ and OH ions unite to form Pure water (de-ionized).
    H+ + OH → H2O

Question 11.
Write a few lines on the utility of hydrogen as a fuel. [AP 17]
Answer:

  1. Hydrogen has high ‘Heat of combustion’. When compared to any other fuels like methane, L.P.G etc. Hence it is used for industrial purposes.
  2. Pollutants in combustion of hydrogen will be less than petrol. The only pollutants will be the oxides of nitrogen and it can be minimised by injecting small amount of water into the hydrogen cylinder.
  3. Hydrogen is used as a rocket fuel.
  4. Hydrogen is used in fuel cells for generating electrical energy.
  5. Atomic hydrogen and oxy hydrogen torches are used for welding and cutting metals.

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 12.
A 1% solution of H2O2 is provided to you. What steps do you take to prepare pure H2O2.
Answer:
To obtain pure H2O2 from the given 1 % H2O2 the following steps are involved.

Step I : Carcful evaporation of the solution
The given 1% H2O2 is carefully evaporated on a water bath under reduced pressure by distillation.
Then 20% – 30% H2O2 solution is obtained.

Step II : Distillation under reduced pressure
The obtained solution in step-1 is heated in a distillation flask at a reduced pressure of 15mm.
Due to this process 85% H2O2 is obtained.

Step III : Crystallization
The sample obtained in step-II is crystallized by freezing.
Then 100% pure hydrogen peroxide is obtained.

Question 13.
Mention any three uses of H202 in modern times. [TS 19]
Answer:

  1. H2O2 is used as antiseptic in medicine and surgery.
  2. H2O2 is used to bleach silk, wool, ivory, hair etc.
  3. H2O2 is used to restore the colour of old and spoiled lead paintings.
  4. H2O2 is used as an oxidising and reducing agent in the laboratory.
  5. 90% solution of H2O2 is used as a fuel in submarines and rockets.

Long Answer Questions

Question 1.
Write an essay on the commercial preparation of dihydrogen. Give balanced equations.
Answer:
Commercially hydrogen is prepared in the following methods.
1) Electrolysis method :
Electrolysis of acidified or alkaline water gives hydrogen.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 10

2) In the electrolysis of brine solution along with NaOH and Cl2, hydrogen is obtained as ‘by product’ at cathode.
Ionisation: 2NaCl → 2Na+ + 2Cl
At anode: 2Cl(aq) → Cl2(g) + 2e (oxidation)
At cathode: 2H2O(l) + 2e → H2(g) + 2OH(aq) (reduction)

3) When coke (or) hydrocarbons react with steam at high temperature in presence of catalysts produces hydrogen.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 11
The mixture of CO and H2 is known as ‘Syngas’.
4) When Syngas mixture reacts with steam in the presence of iron chromate (FeCrO4) gives hydrogen.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 12

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 2.
Illustrate the chemistry of dihydrogen by its reaction with
i) N2
ii) Metal ions and metal oxides and
iii) Organic compounds How is dihydrogen used in the manufacture of chemicals?
Answer:
Chemistry of dihydrogen:
(i) Reaction with N2 :
Hydrogen reacts with Nitrogen in the presence of iron powder as catalyst and forms ammonia.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 13
This reaction is used in the manufacture of ammonia by Haber’s process.

ii) Reaction with metal ions, metal oxides :
Hydrogen is a good reducing agent and reduces several metal oxides and metal ions to their corresponding metals.
Pd2+ + H2 → Pd + 2H+
Cuo + H2 → Cu + H2O

iii) Reaction with Organic compounds:
a) Hydrogenation of oils :
When H2 gas is passed into vegetable oils, in the presence of Ni catalyst, at 5 atm pressure and 473K, Vanaspati is produced.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 14
Vegetable oil +H2 Ni/473K so] fat

b) Hydrofomrylation of alkenes gives aldehydes, which further reacts with H2 and fonns alcohols on reduction.
RCH = CH2 + H2 + CO → RCH2 – CH2CHO
RCH2CH2CHO + H2 → RCH2CH2CH2OH

In Hie manufacture of Chemicals:
Dihydrogen is used in the preparation of so many chemicals like Ammonia, HCl, Methanol,
i) H2 reacts with N2 and forms NH3.( Manufacture of Ammonia by Haber’s process)
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 15
ii) H2 reacts with Cl2 and gives hydrochloric acid.
H2 + Cl2 → 2HCl
iii) Water gas and H2 mixture is passed on ZnO+CrO3 catalyst at 300°C gives Methanol.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 16

Question 3.
Explain, with suitable examples, the following: [IPE’ 14][AP I6][TS 18, 20]
i) Electron deficient ii) Electron-precise and iii) Electron-rich hydrides.
Answer:
i) Electron deficient hydrides :
These hydrides have lesser number of electrons than required for conventional Lewis structure.
Ex: B2H6 (Diborane)
Group 13 elements form such hydrides.

ii) Electron precise hydrides :
These hydrides have exactly the required number of electrons for conventional Lewis structures.
Ex: CH4, SiH4, GeH4 Group 14 elements form such hydrides.

iii) Electron rich hydrides :
These hydrides have excess number of electrons than required for conventional Lewis structure.
Ex: NH3, H2O, HF.
Group 15-17 elements form such hydrides.

The excess number of electrons are present as lone pairs.
Ex: NH3 has 1- lone pair; H2O has 2- lone pairs; HF has 3- lone pairs.

Question 4.
Write in brief on i)ionic hydrides ii)interstitial hydrides [TS 17]
Answer:
i) Ionic hydrides:

  1. Ionic hydrides are formed by the combination of H2 with highly electropositive s-block metals.
  2. These are stoichiometric compounds.
  3. But hydrides such as LiH, BeH2, MgH2 due to polymeric structure have covalent nature.
  4. Usually the ionic hydrides have crystalline structures. They are non-volatile compounds. They are non-conducting in solid state. But in molten condition, if electrolysed, they give metal at cathode and hydrogen at anode.
    Anode: 2H → H2 + 2e
    This reaction confirms that ionic hydrides contain H ion.
  5. Ionic hydrides react violently with water and produces H2 gas.
    NaH + H2O → NaOH + H2
    So ionic hydrides are used as a source of hydrogen.

ii) Interstitial hydrides:

  1. Interstitial hydrides are formed by the combination of H2 with d – block and f – block elements.
  2. The are non stoichiometric hydrides. Ex: LaH2.87 YbH2.55, ZrH1.3-1.75
  3. But metals of 7, 8 and 9 group elements do not form hydrides.
  4. These hydrides conduct electricity and heat but not as efficiently as their parent metals.
  5. Some metals like Pd and Pt absorb large amounts of hydrogen. This property is known as occlusion. This property is also used for storage of H2 and purification of H2.
  6. Absorption of H2 by transition metals is used in catalytic hydrogenation and reduction.

Question 5.
Explain any four of Hie chemical properties of water.
Answer:
1) Amphoteric nature:
Water can act both as acid and base.
In the Bronsted sense, it acts as an acid with NH3 and a base with H2S.
H2O(l) + NH3(aq) ⇌ OH(aq) + NH+4(aq)
H2O(l) + H2S(aq) ⇌ H3O+(aq) + HS(aq)

2) Photosynthesis :
CO2 reacts with H2O in the presence of Chlorophyll and Sunlight forms carbohydrates with the liberation of O2.
6CO2 + 6H2O → C6H2O6 + 6O2

3) Reaction with Metals :
Water reacts with metals and liberates hydrogen.
Here water is reduced to hydrogen and metals are oxidised.
2Na + 2H2O → 2NaOH + H2

4) Reaction with Non Metals: H20 reacts with F2 and it is oxidised to O2.
2F2(g) + 2H2O(l) → 4HF(aq) + O2

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 6.
Explain the terms hard water and soft water. Write a note on the [AP 16, 18, 22]
I) ion-exchange method and [TS 15, 19]
II) Calgon method for the removal of hardness of water.
Answer:
Soft water :
Water which gives lather readily with soap is called soft water.

Soft water is free from dissolved salts of calcium, iron, or magnesium.

Hard water:
Water which do not give lather readily with soap is called hard water. Hardness of water is due to the presence of soluble compounds of magnesium and calcium such as MgCl2, MgSO4, Mg(HCO3)2, CaCl2, CaSO4, Ca(HCO3)2.

AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 17
I) Ion Exchange method:

  1. This method is useful to remove the permanent hardness of water.
  2. It is also named as permutit (or) zeolite process.
  3. Permutit is the artificial zeolite i.e., sodium aluminium orthosilicate (Na2Al2Si2O8. XH2O (or) NaAlSiO4)
  4. Permutit in short form is written as Na2z.
  5. When hard water is passed through permutit, the following ion-exchange reactions take place.
    Na2Z(s) + Ca+2(aq) → CaZ (s) + 2Na+(aq)
    Na2Z(s) + Mg+2(aq) → MgZ(s) + 2Na+(aq)
  6. CaZ and MgZ are called as exhausted permutit. These are regenerated to permutit by the treatment with Brine solution(NaCl).
    CaZ(s) + 2Na+(aq) → Na2Z(s) + Ca+2(aq)

II) Calgon method :
Sodium hexametaphosphate is commercially called as calgon. When calgon is added to hard water it reacts with calcium and magnesium ions forming complex anions.
Na2[Na4(PO3)6] + 2Mg2+ → Na2[Mg2(PO3)6] + 4Na+
Na2[Na4(PO3)6] + 2Ca2+ → Na2[Ca2(PO3)6] + 4Na+

Due to the formation of the complex, the Mg2+ and Ca2+ ions become inactive and cannot react with soap. So the water gives good lather. This method is used only for laundry process.

Question 7.
Write the chemical reaction to justify the hydrogen peroxide can function as on oxidizing as well as reducing agent. [AP 15, 18, 19][TS 16, 18]
Answer:
Hydrogen peroxide can act as both as oxidising and reducing agent in both acid and basic medium. In H2O2 oxidation state of oxygen is -1. Here, it is oxidised to O2. Hence H2O2 is reductant. H2O2 can be reduced to H2O(or) OH. Here H2O2 is oxidant.

As oxidising agent :
H2O2 oxidises black lead sulphide to white lead sulphate.
(a) PbS + 4H2O2 → PbSO4 + 4H2O,
(b) 2Fe2+ + H2O2 → 2Fe3+ + 2OH
(c) Mn2+ + H2O2 → Mn4+ + 2OH,
(d) 2Fe2+ + 2H+ + H2O2 → 2Fe3+ + 2H2O

As reducing agent :
H2O2 reduces acidified potassium permanganate to manganese sulphate.
(a) 2KMnO4 + 3H2SO4 + 5H2O2 → K2SO4 + 2MnSO4 + 8H2O + 5O2
(b) HOCl + H2O2 → Cl + H3O+ + O2
(c) I2 + H2O2 + 2OH → 2I + 2H2O + O2
(d) 2MnO4 + 3H2O2 → 2MnO2 + 3O2 + 2OH + 2H2O

Question 8.
Complete and balance the following chemical reactions:
i) PbS(s) + H2O2(aq) →
ii) MnO4(aq) + H2O2(aq) →
iii) CaO(s) + H2O(g) →
iv) Ca3N2(s) + H2O(l) →
Classify the above into (a) hydrolysis (b) redox and (c) hydration reactions.
Answer:
i) PbS + 4H2O2 → PbSO4 + 4H2O
This reaction is a redox reaction. Here, Pbs is oxidised and H2O2 is reduced.

ii) 2MnO4 + 6H+ + 5H2O2 → 2Mn2+ + 8H2O + 5O2
This reaction is a redox reaction. Here, H2O2 is oxidised and MnO4 is reduced.

iii) CaO(s) + H2O(g) → Ca(OH)2
This reaction is a hydration reaction.

iv) Ca3N2 + 6H2O(g) → 3Ca(OH)2 + 2NH3
This reaction is a hydrolysis reaction.

Question 9.
Discuss, with relevant chemical equations, various methods of preparing hydrogen . peroxide. Which of these methods is useful to prepare D2O2?
Answer:
Preparation of H2O2 :
1) Acidified barium peroxide on removing excess water by evaporation under reduced pressure gives hydrogen peroxide.
BaO2.8H2O(s) + H2SO4 (aq) → BaSO4 + H2O2 (aq) + 8H2O(l)

This BaSO4 can be removed by filtration. Excess water can be removed by evaporation under reduced pressure.

2) Auto oxidation method :
Industrially H2O2 is prepared by the auto oxidation of 2-ethyl anthraquinols.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 18
In this case 1% H2O2 is formed.

3) Electrolysis of 50% H2SO4 using high current density gives peroxodisulphuric acid.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 19

4) Now deuterolysis of peroxodisulphuric acid gives D2O2
K2S2O8 + 2D2O → 2KDSO4 + D2O2
This method is useful to prepare D2O2

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 10.
In how many ways can you express the strength of H2O2? Calculate the strength of 15 volume solution of H2O2 in g/L. Express this strength in normality and molarity.
Answer:
The strength of H2O2 can be expressed in four ways:
(i) Volume strength
(ii) Percentage of Wt.
(iii) Molarity
(iv) Normality

(i) Volume strength: ‘x’ vol. H2O2 means 1 ml of that H2O2 gives ‘x’ ml of O2 at STP.
Ex: 10 vol. H2O2, 20 vol. H2O2 etc.
10 vol. H2O2 solution means 1 ml of this solution liberates 10 ml of O2 gas at STP.

(ii) Percentage of Wt :
‘x’ % (W/V) of H2O2 indicates x gm of H2O2 present in 100ml solution.
Ex: 10 vol. H2O2 = 3.036% (W/V)

(iii) Molarity of H2O2 :
It indicates number of moles of H2O2 in 1 lit solution.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 20
Ex: 10 vol. H202 =0.893M .

(iv) Normality of H2O2 :
It indicates number of gram equivalents of H2O2 present in 1 lit solution.
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 21
Ex: 10 vol. H202=1.786N

Solution to the given problem:
We know the strength of 10 vol. H2O2 is equal to 3% W/V
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 22

Multiple Choice Questions

Question 1.
Radioactive elements emit α, β and γ are characterised by their half lives. The radioactive isotope of hydrogen is
1) Protium
2) Deuterium
3) Tritium
4) Hydronium
Answer:
3) Tritium

Question 2.
Tritium a radioactive isotope of hydrogen, emits which of the following particles?
1) Neutron(n)
2) Beta (β)
3) Alpha (α)
4) Gamma (γ)
Answer:
2) Beta (β)

Question 3.
Which of the following reactions is an example of use of water gas in the synthesis of other compounds?
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 23
Answer:
4

Question 4.
Metal hydrides are ionic, covalent or molecular in nature. Among LiH, NaH, KH, RbH, CsH, the correct order of increasing ionic character is
1) LiH > NaH > CsH > KH>RbH
2) LiH < NaH < KH < RbH < CsH
3) RbH > CsH > NaH > KH > LiH
4) NaH > CsH > RbH > LiH > KH
Answer:
2) LiH < NaH < KH < RbH < CsH

Question 5.
Elements of which of the following group(s) of periodic table do not form hydrides.
1) Groups 7, 8, 9
2) Group 13
3) Groups 15, 16, 17
4) Groupl4
Answer:
1) Groups 7, 8, 9

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 6.
Which of the following reactions increases production of dihydrogen from synthesis gas?
AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 24
Answer:
3

Question 7.
Which of the-following hydrides is electron-precise hydride?
1) B2H6
2) NH3
3) H2O
4) CH4
Answer:
4) CH4

Question 8.
Which of the following statements about hydrogen is incorrect?
1) Hydronium ion, H3O+ exists freely in solution
2) Dihydrogen does not act as a reducing agent
3) Hydrogen has three isotopes of which tritium is the most common
4) Hydrogen never acts as cation in ionic salts.
Answer:
3 And 4

Question 9.
Only one element of _____ forms hydride.
1) group 6
2) group 7
3) group 8
4) group 9
Answer:
1) group 6

Question 10.
Which Of the following ions will cause hardness in water sample?
1) Ca2+
2) Na+
3) Cl
4) K+
Answer:
1) Ca2+

Question 11.
Which of the following compounds is used for water softening?
1) Ca3(PO4)2
2) Na3PO4
3) Na6P6O18
4) Na2HPO4
Answer:
3) Na6P6O18

Question 12.
The method used to remove temporary hardness of water is
1) synthetic resins method
2) Calgon’s method
3) Clark’s method
4) ion-exchange method
Answer:
3) Clark’s method

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 13.
Match the following and identify the correct option

(A) CO(g) + H2(g) (i) Mg(HCO3)2 + Ca(HCO3)2
(B) Temporary (ii) an electron deficient hardness of water hydride
(C) B2H6 (iii) Synthesis gas
(D) H2O2 (iv) Non-planar structure

AP Inter 1st Year Chemistry Important Questions Chapter 7 Chemical Equilibrium and Acids-Bases 25
Answer:
1

Question 14.
Hydrogen peroxide is obtained by the electrolysis of _________
1) water
2) sulphuric acid
3) hydrochloric acid
4) fused sodium peroxide
Answer:
2) sulphuric acid

Question 15.
When sodium peroxide is treated with dilute sulphuric acid, we get
1) sodium sulphate and water
2) sodiun sulphate and oxygen
3) sodium sulphate, hydrogen and oxygen
4) sodium sulphate and hydrogen peroxide
Answer:
4) sodium sulphate and hydrogen peroxide

Question 16.
Hydrogen peroxide is
1) an oxidising agent
2) a reducing agent
3) both an oxidising and a reducing agent
4) neither oxidising nor reducing agent
Answer:
3) both an oxidising and a reducing agent

Question 17.
Which’of the following equations depict the oxidising nature of H2O2?
1) 2MnO4 + 6H+ + 5H2O2 → 2Mn2+ + 8H2O + 5O2
2) 2Fe+32H+ +H2P2 → 2Fe2+ +2H2O + O2
3) 2I + 2H+ + H2O2 → I2 + 2H2O
4) KIO4 + H2O2 . KIO3 + H2O + O2
Answer:
3) 2I + 2H+ + H2O2 → I2 + 2H2O

Question 18.
Which of the following equation depicts reducing nature of H2O2?
1) 2[Fe(CN)6]4- + 2H+ + H2O2 → 2[Fe(CN)6]3- + 2H2O
2) I2 + H2O2 + 2OH → 2I + 2H2O + O2
3) Mn2+ + H2O2 → Mn4+ + 2OH
4) PbS + 4H2O2 → PbSO4 + 4H2O
Answer:
2) I2 + H2O2 + 2OH → 2I + 2H2O + O2

Question 19.
The oxide that gives H2O2 on treatment with dilute H2SO4is
1) PbO2
2) BaO2.8H2O + O2
3) MnO2
4) TiO2
Answer:
2) BaO2.8H2O + O2

AP Inter 1st Year Chemistry Important Questions Chapter 8 Hydrogen and its Compounds

Question 20.
Some statements about heavy water are given below:
A) Heavy water is used as a moderator in nuclear reactors
B) Heavy water is more associated than ordinary w;ater
C) Heavy water is more effective solvent than ordinary water
Which of the above statements are correct?
1) A and B
2) A, B and C
3) B and C
4) A and C
Answer:
1) A and B

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