Study of Compounds – Ammonia Quiz - ICSE Class 10 Chemistry
Free practice quiz: Study of Compounds – Ammonia (ICSE Class 10 Chemistry). 12 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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Which of the following is a characteristic of the 'brown ring test' for nitrates and nitrites, which involves ammonia?
- The brown ring is formed by the formation of a complex between Fe(II) and NO.
- The brown ring is formed by the formation of a complex between Fe(III) and NO.
- The brown ring is formed by the precipitation of iron (II) hydroxide.
- The brown ring is formed by the reaction of ammonia with nitric acid.
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Answer: A. The brown ring is formed by the formation of a complex between Fe(II) and NO.
The brown ring test for nitrates involves the formation of a complex, [Fe(NO)(H₂O)₅]²⁺, which is brown. This complex is formed from Fe²⁺ ions (obtained by reducing nitrates), nitric oxide (NO, produced from the reduction of nitrate in acidic medium), and water molecules. Ammonia's role in some variations is to ensure an alkaline environment or as a source of nitrogen in other tests, but the core brown ring formation is about Fe(II) and NO.
What is the role of iron catalyst in the Haber process?
- To increase the yield of ammonia.
- To increase the rate of reaction without affecting the equilibrium position.
- To shift the equilibrium towards reactants.
- To absorb water from the reaction mixture.
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Answer: B. To increase the rate of reaction without affecting the equilibrium position.
Catalysts increase the rate of both forward and reverse reactions equally. Therefore, they help in reaching the equilibrium faster but do not change the position of the equilibrium itself, and thus do not affect the final yield of ammonia at equilibrium.
Which of the following tests uses ammonia solution to detect the presence of specific metal ions by forming a precipitate?
- Baeyer's test
- Fehling's test
- Tests for metal hydroxides
- Liebig's test
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Answer: C. Tests for metal hydroxides
Ammonia solution is a mild base that precipitates metal hydroxides. The formation or non-formation of a precipitate, and its solubility in excess ammonia, are used to identify certain metal ions. For example, Zn²⁺ precipitates as Zn(OH)₂ but redissolves in excess ammonia due to complex formation.
In the laboratory preparation of ammonia, the gas is collected by upward displacement of air. This method is used because:
- Ammonia is lighter than air.
- Ammonia is heavier than air.
- Ammonia is highly soluble in water.
- Ammonia is less soluble in water.
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Answer: A. Ammonia is lighter than air.
Ammonia has a molecular weight of 17 g/mol, while the average molecular weight of air is about 29 g/mol. Therefore, ammonia is lighter than air and can be collected by upward displacement of air (also known as downward delivery). It is also highly soluble in water, so collection over water is not feasible.
Which of the following statements about the industrial production of ammonia via the Haber process is correct regarding the catalyst and conditions?
- Iron catalyst is used at low temperature and high pressure.
- Iron catalyst is used at high temperature and low pressure.
- Iron catalyst with promoters is used at moderate temperature and high pressure.
- Platinum catalyst is used at low temperature and low pressure.
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Answer: C. Iron catalyst with promoters is used at moderate temperature and high pressure.
The Haber process uses an iron catalyst promoted with substances like potassium oxide (K₂O) and aluminum oxide (Al₂O₃). The process is carried out at a temperature of around 400-450°C (moderate temperature) and pressures of 150-350 atmospheres (high pressure) to achieve a reasonable rate of reaction and a good yield of ammonia.