Preparation of Dihydrogen - UNSOLVED PRACTICE SET
Chapter: Hydrogen | Topic: Preparation of Dihydrogen
PREPARATION OF DIHYDROGEN - UNSOLVED PRACTICE SET
Topic: Preparation of Dihydrogen
Multiple Choice Questions
Q1. In the laboratory, dihydrogen is commonly prepared by the reaction of:
- Zinc with concentrated nitric acid
- Zinc with dilute hydrochloric acid
- Sodium with water
- Iron with concentrated sulphuric acid
Q2. Which of the following metals cannot be used for laboratory preparation of H₂ with dilute HCl?
- Zn
- Fe
- Cu
- Mg
Q3. The reaction of steam with red hot iron is called:
- Bosch process
- Lane's process
- Haber's process
- Contact process
Q4. In the electrolysis of water for preparing hydrogen, the gas collected at the cathode is:
- Oxygen
- Hydrogen
- Both in equal amounts
- No gas is evolved
Q5. For commercial production, hydrogen is obtained from water gas by reacting it with:
- Carbon dioxide
- Steam
- Hydrogen sulphide
- Nitrogen
Q6. In your school laboratory, if you add zinc to very dilute nitric acid, you are likely to get:
- Hydrogen gas
- Nitric oxide
- Ammonium nitrate
- Both (b) and (c), but not hydrogen
Short Answer Questions
Q7. Write balanced chemical equations for the preparation of dihydrogen by:
(a) Reaction of zinc with dilute sulphuric acid
(b) Reaction of steam with red hot coke
Q8. Why is dilute nitric acid not used for the laboratory preparation of hydrogen, even though it is an acid?
Q9. Explain the principle behind the electrolysis of acidified water for hydrogen production. Why is a small amount of acid (like H₂SO₄) added to water?
Q10. In the commercial preparation of hydrogen from water gas (CO + H₂), how is pure hydrogen separated? Write the relevant chemical equation.
Q11. Your friend suggests using sodium metal instead of zinc to prepare hydrogen in the school lab. Why is this not a practical idea for routine laboratory preparation?
Q12. What is the role of a catalyst in the preparation of hydrogen from hydrocarbons? Name one catalyst used in steam reforming of methane.
Long Answer Questions
Q13. Describe the laboratory method for the preparation of dihydrogen. Include:
(a) The apparatus setup (Kipp's apparatus or simple flask method)
(b) The choice of metal and acid
(c) Why the gas is collected by downward displacement of water
(d) How you would test for the purity of hydrogen gas
Q14. Discuss the commercial methods for the preparation of hydrogen:
(a) From water gas (Bosch process)
(b) By electrolysis of water
(c) From hydrocarbons (steam reforming)
Compare these methods in terms of purity of hydrogen obtained and energy requirements.
Q15. Hydrogen is being produced on a large scale for use in hydrogen fuel stations in countries like Japan and Germany. Discuss the challenges of producing hydrogen on an industrial scale for India's future energy needs. What methods would be most suitable for India and why?
Numerical / Application-Based Problems
Q16. In a school experiment, 13 g of zinc granules are added to excess dilute hydrochloric acid.
(a) Calculate the volume of hydrogen gas evolved at STP.
(b) If the same mass of magnesium is used instead, how would the volume of hydrogen change? Calculate the new volume.
[Given: Atomic masses: Zn = 65 u, Mg = 24 u; Molar volume at STP = 22.4 L]
Q17. In the electrolysis of water, a current of 2 A is passed for 30 minutes.
(a) Calculate the total charge passed.
(b) Using Faraday's laws, calculate the mass of hydrogen liberated at the cathode.
(c) What volume would this hydrogen occupy at STP?
[Given: 1 F = 96500 C, Molar mass of H₂ = 2 g/mol]
Q18. A water gas sample contains CO and H₂ in a 1:1 molar ratio. 100 L of this water gas at STP is passed over heated Fe₃O₄ to remove CO.
(a) Write the balanced equation for the reaction.
(b) Calculate the volume of pure hydrogen obtained after the reaction.
(c) If this hydrogen is used to fill balloons, and each balloon requires 10 L of H₂ at STP, how many balloons can be filled?