Eau = H2O
Masse molaire de l'eau = 2M(H) + M(O) = 2+16 = 18 g/mol
Masse volumique de l'eau = 1000 g/L
n = m/M
Or ρ = m/V donc m = ρV
Donc n = ρV/M = 1000x1/18 = 56 mol