a) MCO = 28g/mol
n = m/M = 2,8/28 = 0,1 moli CO
1 mol CO............N.A atomi = 6,022×10^23 atomi
0,1 moli CO.........................x = 6,022×10^22 atomi
b) MH2O = 18g/mol
n = m/M = 36/18 = 2 moli H2O
nr atomi H2O = 2×N.A = 2×6,022×10^23 = 1,2044×10^24