1. The equation of interaction of sodium hydroxide with phosphoric acid has the form:
3NaOH + H3PO4 = Na3PO4 + 3H2O;
2.Calculate the chemical amount of sodium hydroxide:
n (NaOH) = m (NaOH): M (NaOH);
M (NaOH) = 23 + 16 + 1 = 40 g / mol;
n (NaOH) = 20: 40 = 0.5 mol;
3. Determine the amount of water formed:
n (H2O) = n (NaOH) = 0.5 mol;
4.calculate the mass of water:
m (H2O) = n (H2O) * M (H2O);
M (H2O) = 2 + 16 = 18 g / mol;
m (H2O) = 0.5 * 18 = 9 g;
Answer: 9 g.
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