CAPF AC 2025 Q103: Science & Technology – Biology

CAPF AC 2025, Paper I (General Ability and Intelligence) · Science & Technology

Consider the following statements : 1. The circulation of nitrogen from the inorganic compounds in the soil to form protein in plants and animals and back again is known as the nitrogen cycle. 2. The preparation of ammonia by Haber process is an endothermic reaction. 3. Urea is synthetically made by the action of ammonia and carbon dioxide under high temperature and high pressure. Which of the statements given above is/are not correct?

(a) 1 and 3
(b) 2 and 3
(c) 2 only
(d) 1 only

Answer: (c) 2 only

Explanation

Nitrogen cycle, Haber process and urea

How to think: the question asks which statement(s) are not correct.

Statement	Fact	Verdict
1. Circulation of nitrogen from soil compounds into plants and animals and back is the nitrogen cycle	That is the definition of the nitrogen cycle	Correct
2. Haber process for ammonia is endothermic	N₂ + 3H₂ gives 2NH₃ with ΔH = -92 kJ, so it is exothermic	Not correct
3. Urea is made from ammonia and carbon dioxide at high temperature and pressure	2NH₃ + CO₂ gives urea (NH₂CONH₂) + H₂O under those conditions	Correct

Only statement 2 is not correct.

Bank key corrected: the stored key was (b) 2 and 3; statement 3 is correct, so the right answer is (c).

Answer: (c) 2 only.

Why each option is right or wrong

(a) Incorrect. Statements 1 and 3 are both correct.
(b) Incorrect. Statement 3 is correct, so it cannot be in the 'not correct' set.
(c) CORRECT. Only statement 2 is not correct: the Haber process is exothermic.
(d) Incorrect. Statement 1 is correct.

Key point

Haber process: N₂ + 3H₂ ⇌ 2NH₃, ΔH = -92 kJ, exothermic; 200 atm, 450 °C, iron catalyst. Urea: ammonia + CO₂ at high temperature and pressure (Bosch-Meiser). Nitrogen cycle: fixation, nitrification, assimilation, ammonification, denitrification.

Remember

Haber process is exothermic; high temperature is used for speed, not because it needs heat.

Common mistakes

Thinking the Haber process is endothermic because it needs high temperature.
Marking the urea statement wrong because urea is found in urine.
Missing the word not in the question.

Exam tip

Educated guess: statements 1 and 3 read like textbook definitions. The Haber process is a classic exothermic equilibrium, so statement 2 is the odd one.

Sources

NCERT Class XI Chemistry, Part II, Chapter 7 (Equilibrium: Haber's process)
NCERT Class XI Biology, Chapter 12 (Mineral Nutrition: the nitrogen cycle)

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