(i) Molar mass of ethyl alcohol (C2H5OH) is 46 g/mol
So, 46 g of ethyl alcohol will have 6.023 × 1023 molecules,
(ii) Molar mass of nitrogen pentaoxide (N2O5) is 108 g/mol
So, 54 g of N2O5 will contain 1/ 2 mole
i.e., 6.023 × 1023 × (1/2) molecules.
= 3.0115 × 1023 molecules
Hence, 54 g of nitrogen pentaoxide will have minimum number of molecules.