The question seems to be confusing but what I understood is that we are asked the number of moles for 40 g of H2O. The molar mass of H2O is the some of the atomic masses of the elements involved which would be 18.02 g/mol
40 g H2O ( 1 mol / 18.02 g ) = 2.22 mol H2O
Hope this answers the question. Have a nice day.
