Calculate the mass: 0.3 mol H2O. 0.5 mol KCl. 4 mol CuO. 0.2 mol Re2O3.

To calculate the mass of a substance, we use the formula: m = V x M, where m is the mass of the substance, V is the number of moles of the substance, M is the molar mass of the substance.
1.m H2O = 0.3 x 18 = 5.4 g;
2.m KCl = 0.5 x 74.55 = 37.3 g;
3.m CuO = 4 x 79.5 = 318 g;
4.m Re2O3 = 0.2 x 420.41 = 84.1 g.