Which contains more molecules, 10 g of sulphur dioxide (SO2) or 10 g of oxygen (O2)?
(Atomic masses: S = 32 u; O = 16 u)
Molar mass of SO2 = (32 + 2×16) g = 64g
Given mass of SO2 = 10g
1 mole of substance = 6.023 × 1023 particles of the substance
No. of moles of SO2 = 10g/64g = 0.15
Total no. of molecules of SO2 = 0.15 × 6.022 × 1023 = 0.90 × 1023 molecules of SO2
Molar mass of oxygen (O2) = 32g
Given mass of oxygen (O2) = 10g
1 mole of substance = 6.023 × 1023 particles of the substance
No. of moles of O2 = 10g/32g = 0.31
Total no. of molecules of O2 = 0.31 × 6.022 × 1023 = 1.88 × 1023 molecules of O2
Thus, 10g of O2 contains more no. of molecules.