Which one of the following would have highest number of molecules?

The number of molecules in a given mass is determined by the formula: Number of molecules = (Mass / Molar mass) × Avogadro's number [t1][t2]. To find the highest number of molecules, we compare the number of moles for each option. (1) 10 g of CO2: Molar mass is 44 g/mol [t5][t7], giving 10/44 ≈ 0.227 moles. (2) 10 g of O2: Molar mass is 32 g/mol [t1], giving 10/32 ≈ 0.312 moles. (3) 5 g of NH3: Molar mass is 17 g/mol [t4], giving 5/17 ≈ 0.294 moles. (4) 1 g of H2: Molar mass is approximately 2 g/mol (since H is ~1 g/mol) [t6][t7], giving 1/2 = 0.5 moles. Since 1 g of hydrogen yields the highest number of moles (0.5), it contains the highest number of molecules [t8].