What is the mass of 0.5 mole of Cl 2 gas?
Mass of one chlorine molecule is 35.5 x 2 i.e. 71
One mole of chlorine = 6.023 xx 1023 chlorine molecules
Therefore mass of one mole of chlorine molecule = 6.023 xx 1023 x 71
Therefore 0.5 mole of Cl2 = 6.023 xx 1023 x 71 x 0.5
= 213.8165 x 1023