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Hydrogen and its Compounds Important Questions And Answers

 Hydrogen and its Compounds Important Questions And Answers

Hydrogen and its Compounds is the most important and interesting chapter of Chemistry. So the practice set of Hydrogen and its Compounds with Important Questions And Answers helps students of class 11 and also for students studying for various competitive exams. Students are advised to practice and understand all the questions accordingly.

Hydrogen and its Compounds Important Questions And Answers

1.Which is used as hydrogen generators:

a) NaH

b) Hi

c) S6H3

d) None of these


NaH + H2O → NaOH + H2

2.Hydrogen burns in air with a:

a) Light bluish flame

b) Yellow flame

c) Green flame

d) None of these

3.Which is distilled first.

a) Liquid CO2

b) Liquid N2

c) Liquid O2

d) Liquid H2


Boiling point of liquid hydrogen is lowest of given substances so it is distilled first.

4.On reaction with Mg, very dilute nitric acid produces.

a) NH3

b) Nitrous oxide

c) Nitric oxide

d) Hydrogen


Mg + 2HNO3 → Mg(NO3)2 + H2

5.Which of the following reaction produces hydrogen

a) Mg + H2O

b) BaO2 + HCl

c) H2S4O8 + H2O

d) Na2O2+2HCl


Mg + 2H2O → Mg(OH)2 + H2

6.The nuclei of tritium (H3) atom would contain neutrons

a) 1

b) 2

c) 3

d) 4


Number of neutrons =  Mass number – Atomic number

= 3 – 1 = 2

7. Which isotope of hydrogen is used as a trace in organic reactions?


Hydrogen has three isotopes, H, D and T. Due to differences in masses, the rate constants of three isotopes with the same substance are different. In other words, both D and T show isotopic effect. But since T is not only radioactive but is also least abundant hydrogen isotope. Therefore D is used as a trace to study the mechanism of organic reactions.

8.Ordinary hydrogen at room temperature is a mixture of

a) 75% of o-Hydrogen + 25% of p-Hydrogen

b) 25% of o-Hydrogen + 75% of p-Hydrogen

c) 50% of o-Hydrogen + 50% of p-Hydrogen

d) 1% of o-Hydrogen + 99% of p-Hydrogen

9. The adsorption of hydrogen by metals is called

a) Dehydrogenation

b) Hydrogenation

c) Occlusion

d) Adsorption


Occlusion is the phenomenon of adsorption of hydrogen by metal.

10.Which of the following produces hydrolith with dihydrogen

a) Mg

b) Al

c) Cu

d) Ca


CaH2 is known as hydrolith.

11.Metals like platinum and palladium can absorb large volumes of hydrogen under special conditions. Such adsorbed hydrogen by the metal is known as:

a) Adsorbed hydrogen

b) Occluded hydrogen

c) Reactive hydrogen

d) Atomic hydrogen


Occluded hydrogen is the hydrogen absorbed by the metal.

12.The difference between heat of adsorption of ortho and para hydrogen is

a) 0.4 kJ mol-1

b) 0.8kJ mol-1

c) Zero

d) None of these

13.Cu does not liberate H2 from dil H2SO4. Explain.


Cu is placed below H in electrochemical series having oxidation potential -0.34 V hence Cu can not transfer electron to H+ ions of H2SO4 to liberate H2.

14.When electric current is passed through an ionic hydride in the molten state

a) Hydrogen is liberated at the anode.

b) Hydrogen is liberated at the cathode.

c) No reaction takes place

d) Hydride ion migrates towards cathode.


M+ H → M+  + H   H → \(\frac{1}{2}\) H2 + e  (at anode)

15.Hydrogen acts as a reducing agent and thus resembles

a) Halogen

b) Noble gas

c) Radioactive elements

d) Alkali metals


Alkali metals are good reducing agents because of low ionization energy and hydrogen also shows same character.

16.The ratio \(\frac{Cp}{Cv}\) for H2 is

a) 1.40

b) 1.67

c) 1.33

d) None of these.


For diatomic gases (e.g. H2) r = \(\frac{Cp}{Cv}\)

=1.40 For monoatomic gases r =1.66 For triatomic gases r =1.33

17.Synthetic detergents are more effective in hard water than soaps because

a) They are highly soluble in water

b) Their Ca++ and Mg++ salts are water soluble

c) Their Ca++ and Mg++ salts are insoluble in water

d) None of these

18.D2O is used more in

a) Chemical industry

b) Nuclear reactor

c) Pharmaceutical preparations

d)  Insecticide preparation

19. The velocity of neutrons in nuclear reactor is slowed down by

a) Heavy water (D2O)

b) Ordinary water (H2O)

c) Zinc rod

d) Fused caustic soda


Heavy water i.e., D2O slows down the speed of neutrons in nuclear reactors.

20. Cu is placed below H in electrochemical series having oxidation potential -0.34 V hence Cu can not transfer electron to H+ ions of H2SO4 to liberate H2. Why is hard water softened before its use in boilers?


Hard water cannot be used in boilers because on heating it gives precipitates of CaCO3 and MgCO3 along with CaSO4 which forms scales in boilers. To avoid the scales formation, hard water is softened before its use in boiler.

21.The molarity of pure water at 4C is

a) 1 M

b) 2.5 M

c) 5 M

d) 55.5 M


The density of water is 1 gcm−3 at 4°C

so molarity = \(\frac{1000}{18}\) =55.5M.

22. What volume of oxygen at NTP will be obtained by the complete decomposition of 100 ml of H2O2 marked 30 volume?


1 ml H2O2 of 30 volume liberates 30 ml O2 at NTP.

100 ml H2O2 of 30 volumes liberate 30

100 ml O2 at NTP or 3 litre O2­ at NTP.

23.Permutit is a technical name given to

a) Aluminates of calcium and sodium

b) Silicates of calcium and sodium

c) Hydrated silicates of aluminium and sodium

d) Silicates of calcium and magnesium


It is Na2Al2Si2O8.xH2O

24.The alum used for purifying water is

a) Ferric alum

b) Chrome alum

c) Potash alum

d) Ammonium alum


K2SO4.Al2(SO4)3 . 24H2O Potash alum is generally used for purifying water.

25. Pure water can be obtained from sea water by

a) Centrifugation

b) Plasmolysis

c) Reverse osmosis

d) Sedimentation


Pure water can be obtained from sea water by reverse osmosis.

26.What happens when Zn reacts with H2SO4? Explain.


Whenever a metal reacts with a acid it gives salt + hydrogen gas so in this case zinc reacts with H2SO4 so as a result of it it will give zinc sulphate with the evolution of hydrogen gas

27. Hydrogen peroxide is reduced by

a) Ozone

b) Barium peroxide

c) Acidic solution of KMnO4

d) Lead sulphide suspension


PbS + 4H2O2 → PbSO4 + 4H2O

29.Hydrogen peroxide is used as

a) Oxidising agent

b) Reducing agent

c) Both as oxidising and reducing agent

d) Drying agent

30.Kα of H2O2 is of the order of

a) 10−12

b) 10−14

c) 10−16

d) 10−10


Kα of H2O= 1.55  × 10−12 

31.The volume of oxygen liberated from 0.68gm of H2O2 is

a) 112ml

b) 224ml

c) 56ml

d) 336m


We know that 2H2O2  →  2H2O + O2

2 × 34g in 22400ml

∵ 2 × 34gm = 68gm of H2O2 liberates 22400ml O2 at STP

∴ .68gm of H2O2 liberates

= 68 × 2240/068 = 224ml

32.The structure of H2O2 is

a) Open book like

b) Linear

c) Closed book

d) Pyramidal

33.HCl is added to following oxides. Which one would give H2O2

a) MnO2

b) PbO2

c) BaO

d) None of these


MnO2, PbO2 and BaO will not give H2O2 with HCl.MnO2 and PbO2 will give Cl2 and BaO will react with HCl to give BaCl2 and water.

34. A commercial sample of hydrogen peroxide is labelled as 10 volume. Its percentage strength is nearly

a) 1%

b) 3%

c) 10%

d) 90%


10 volume solution of H2O2 is 3.035% solution i.e., 3.035 g of H2O2 is present in 100ml of the solution.

35.H2O2 is a very good solvent for ionic compounds.Explain.


The dielectric constant of pure H2O2 is 93.7 (which also increases on dilution (97 for 90% pure; 120 for 65% pure) which is appreciably high to weaken the electrostatic forces of attraction among ions and to pass them in solution state.

36.A sample of water containing some dissolved table sugar and common salt is passed through organic ion exchange resins.The resulting water will be

a) Tasteless

b) Sweet

c) Salty

d) None of these


Organic ion exchange resins can remove only ionic impurities.

37.The hardness of water sample containing 0.002 mole of magnesium sulphate dissolved in a litre of water is expressed as:

a) 20 ppm

b) 240 ppm

c) 2000 ppm

d) 120 ppm

38.Difference between Atomic hydrogen and Nascent hydrogen.


Atomic hydrogen Nascent hydrogen
It is very reactive and its half-life period is 0.33 s. Freshly prepared hydrogen is known as nascent hydrogen and is more reactive than ordinary hydrogen

39. How many hydrogen-bonded water molecule(s) are associated in CuSO4. 5H2O?


Only one water molecule, which is outside the brackets (coordination sphere), is hydrogen-bonded. The other four molecules of water are coordinated.

40.Photohydrogen is :

a) Obtain renewable energy from sunlight by using microscopic organism such as bacteria or algae.

b)  Obtain renewable energy from sunlight by using microscopic organism such as bacteria or fungi

c) both of above

d) none of these

41.Describe some important Uses of Dihydrogen


  • In the manufacture of CH3OH.
  • We use liquid hydrogen (LH2) in fuel
  • The largest single use of H2 is in the synthesis of NH3 which is used in the manufacture of HNO3 and fertilizers.
  • We use liquid hydrogen (LH2) in fuel.
  • H2 is used as a reducing agent in extraction of metals.
  • H2 is used in fuel cell for generating electrical energy.
  • We is used in the manufacture of synthetic petrol.
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