Calculate -
(a) The number of molecules of sulphur (S8) in 16 g of solid sulphur.
(b) Number of moles in 20 g of water.
a) Molar mass of S8 = 256 g mol-1
We know,
1 mole of S8 = Molar mass of S8 = 6.022 x 1023 molecules
256 g of S8 = 6.022 x 1023 molecules
Therefore, 16 g of S8 contains 3.76 x 1022 molecules.
(b) Molar mass of water (H2O)
= (2 x atomic mass of H) + (1 x atomic mass of O)
= (2 x 1) + 16
= 18 g
18 g of water = 1 mole
