What is the mass of 4 moles of water?

Explanation of the solution to the problem: to solve this problem, you must use the following formula:
m = n * M, where n is the amount of a given substance (in this case, the number of moles of water), mol; M is the molar mass of the substance, M (H2O) = 18 g / mol (according to the table of chemical elements by D. I. Mendeleev); m is the mass of the substance, g.
Substituting the values known from the condition of the problem into the formula, we obtain:
m (H2O) = n (H2O) * M (H2O) = 4 mol * 18 g / mol = 72 g.