Which one of the following statements is NOT correct ?

At Standard Temperature and Pressure (STP), one mole of any gas occupies 22.4 litres and contains Avogadro's number of molecules (6.022 × 10²³). Statement 1 is correct because half a mole of nitrogen gas occupies 11.2 litres (22.4 / 2). Statement 2 is correct as the molar mass of ammonia (NH₃) is 17 g (N=14, H=3), which equals one mole and thus contains 6.022 × 10²³ molecules [1]. Statement 3 is correct because 22.4 litres of CO₂ at STP represents one mole, which has a molar mass of 44 g (C=12, O=32). Statement 4 is incorrect because the molar mass of hydrogen gas (H₂) is 2 g. Therefore, 4 grams of hydrogen gas equals 2 moles, which would contain 2 × 6.022 × 10²³ molecules, not 6.022 × 10²³.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 4: Carbon and its Compounds > 4.1 BONDING IN CARBON – THE COVALENT BOND > p. 60