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Q.31. Number of atoms in the following samples of substances is largest in: (1) 4.0 g of hydrogen (2) 71.0 g of chlorine (3) 127.0 g of iodine (4) 48.0 g of magnesium

1. 4.0 g of hydrogen
2. 71.0 g of chlorine
3. 127.0 g of iodine
4. 48.0 g of magnesium

Correct answer: 4.0 g of hydrogen

Solution

The number of atoms in a sample is determined by the number of moles, which is calculated using the formula: moles = mass (g) / molar mass (g/mol). Hydrogen has a very low molar mass (approximately 1 g/mol), so 4.0 g of hydrogen contains a significantly larger number of moles—and thus atoms—compared to the other substances listed.

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