Which one of the following statements is NOT correct?
A.Half mole of nitrogen gas is measured 11·2 litre at STP
B.17 gram of ammonia gas contains 6·022 × 10²³ molecules at STP
C.22·4 litre of CO₂ gas at STP contains 44 gram of molecules
D.4 gram of hydrogen gas contains 6·022 × 10²³ molecules✓ Correct
Explanation
Statement (d) is incorrect. Hydrogen gas (H₂) has a molar mass of 2 g/mol, so 2 grams of H₂ contains 6.022 × 10²³ molecules (Avogadro's number). Therefore, 4 grams of hydrogen gas contains 2 × 6.022 × 10²³ = 1.2044 × 10²⁴ molecules, not 6.022 × 10²³. Statement (a) is correct: 1 mole of any gas at STP occupies 22.4 L, so half a mole occupies 11.2 L. Statement (b) is correct: ammonia (NH₃) has molar mass 17 g/mol, so 17 g contains 6.022 × 10²³ molecules. Statement (c) is correct: 22.4 L of any gas at STP is 1 mole, and CO₂ has molar mass 44 g/mol.
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