Find the mass of water that forms when 30 grams of 40% phosphoric acid solution with sodium hydroxide are poured?

H3PO4 + 3NaOH = Na3PO4 + 3H2O.
Algorithm for solving the problem:
1 Calculation of the mass of the dissolved substance of phosphoric acid in its solution.
2 Calculation of the amount of phosphoric acid substance.
3 Calculation of the amount of water substance.
4 Calculation of the mass of water.
Decision:
1 30 * 40/100% = 12g.
2 12 / (3 * 1 + 31 + 4 * 16) = 12/98 = 0.12 mol.
3 According to the reaction equation, there are three moles of water per mole of acid. This means that the amount of water substance is 0.12 / 3 = 0.04 mol.
4 The mass of water is found by multiplying the amount of water substance by its molar mass: 0.04 * (1 * 2 + 16) = 0.04 * 18 = 0.72g – the answer.