What mass of water forms when 2.75 104 mol NaOH reacts completely?

To make water using NaOH, you can react it with an acid, such as HCl. The reaction is
NaOH + HCl ---> NaCl + H2O. 2.75x10^4 moles of NaOH will produce 2.75x10^4 moles of water because the ratio of NaOH to H2O is 1 to 1 (see equation). Thus, the mass of water formed will be
2.75x10^4 moles H2O x 18 g/mole = 4.95x10^5 grams of water (495 kg)