In what mass of water should 14.2 phosphorus (V) oxide be dissolved so that there are 10 water

In what mass of water should 14.2 phosphorus (V) oxide be dissolved so that there are 10 water molecules for each H3PO4 molecule?

1) Calculate the number of moles of phosphorus oxide: M (P2O5) = 284 g / mol, n (P2O5) = 14.2 / 284 = 0.05 mol;
2) Calculate the number of moles of phosphoric acid: n (H3PO4) = 2 * n (P2O5) = 2 * 0.05 = 0.1 mol;
3) Determine the amount of water required for the reaction with phosphorus oxide: n (H2O) = 3 * n (P2O5) = 3 * 0.05 = 0.15 mol;
4) Determine the total amount of moles of water: n (H2O total) = 0.15 + 0.1 * 10 = 1.15 mol;
5) Calculate the mass of water: M (H2O) = 18 g / mol, m (H2O) = 18 * 1.15 = 20.7 g;
Answer: 20.7 g