Vidaara.orgClass 11 · Chemistry
CodeVID-C11-09-T1-01
Assignment — Hydrogen: Position, Isotopes & Preparation
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- All questions are compulsory.
- Section A carries 1 mark each, Section B 2 marks, Section C 3 marks and Section D 5 marks.
- Write balanced equations wherever required. Only final answers are given at the end — for full solutions, raise your doubts with your teacher.
Section A — Multiple Choice Questions
5 × 1 = 5 marks
1.
The electronic configuration of hydrogen is:
- A.1s2
- B.1s1
- C.2s1
- D.1s12s1
2.
The isotope of hydrogen present in heavy water is:
- A.protium
- B.deuterium
- C.tritium
- D.none
3.
Dihydrogen is collected in the laboratory by:
- A.upward displacement of air
- B.downward displacement of water
- C.displacement of mercury
- D.liquefaction
4.
The catalyst used in the water-gas shift reaction is:
- A.nickel
- B.platinum
- C.iron chromate
- D.manganese dioxide
5.
Hydrogen forms the hydride ion, resembling the:
- A.alkali metals
- B.halogens
- C.noble gases
- D.alkaline earth metals
Section B — Short Answer (2 marks)
3 × 2 = 6 marks
6.
Why is hydrogen not free in the Earth's atmosphere but abundant in combined form?
7.
Write the two reactions used to obtain pure dihydrogen from coke and steam.
8.
Give two ways in which the isotopes of hydrogen differ.
Section C — Short Answer (3 marks)
2 × 3 = 6 marks
9.
Explain, with examples, the diagonal/dual character of hydrogen in the periodic table.
10.
Describe the laboratory preparation of dihydrogen and how it is collected.
Section D — Long Answer (5 marks)
1 × 5 = 5 marks
11.
Discuss the commercial methods of preparing dihydrogen and compare their purity and cost.
Answer Key
Section A — Multiple Choice Questions
- (B) 1s1
- (B) deuterium
- (B) downward displacement of water
- (C) iron chromate
- (B) halogens
Section B — Short Answer (2 marks)
- Hydrogen is so light that the Earth's gravity cannot hold it, so it escapes; in combined form it is locked in water, acids and hydrocarbons, which makes it abundant.
- C + H2O → CO + H2 (water gas); then CO + H2O → CO2 + H2 (shift reaction), and CO2 is scrubbed out.
- They differ in the number of neutrons (0, 1, 2) and in physical properties such as mass, density and rate of reaction; tritium also differs by being radioactive.
Section C — Short Answer (3 marks)
- Like alkali metals it has ns1 configuration, forms H+ and is a reducing agent; like halogens it is one electron short of a noble gas, is diatomic (H2), forms H− and has high ionisation enthalpy. Because it fits neither group perfectly, it is placed separately.
- Granulated zinc is treated with dilute sulphuric acid: Zn + H2SO4 → ZnSO4 + H2. The gas is dried and, being insoluble in water, is collected by downward displacement of water.
Section D — Long Answer (5 marks)
- Electrolysis of warm acidified (or Ba(OH)2) water gives very pure H2 at the cathode but is expensive due to high electricity use. The water-gas route, C + H2O → CO + H2 at 1270 K followed by the shift reaction CO + H2O → CO2 + H2 over iron chromate and CO2 scrubbing, is cheaper and used on a large industrial scale but needs purification. Hydrogen is also obtained as a by-product of the electrolysis of brine and from the steam reforming of hydrocarbons.
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