Phosphorus (V) oxide with a mass of 21.3 g was dissolved by heating in water

Phosphorus (V) oxide with a mass of 21.3 g was dissolved by heating in water. Determine the mass of phosphoric acid in the resulting solution.

Phosphorus (V) oxide
P2O5 phosphorus (V) oxide is a white powder with hygroscopic properties. Phosphorus (V) oxide reacts very vigorously with water. The reaction proceeds very violently with a loud noise accompaniment. It also takes water vigorously from other compounds. Phosphorus (V) oxide is a powerful drying agent.

Orthophosphoric acid
Reacting with water, P2O5 forms H3PO4 – orthophosphoric acid.

P2O5 + 3H2O = 2H3PO4.

Phosphoric acid is a colorless viscous syrupy liquid in appearance. This acid has no smell.

Determination of the mass of phosphoric acid
Based on the data from the periodic table, we calculate the molar masses of phosphorus oxide and orthophosphoric acid. For phosphorus oxide: 31 * 2 + 5 * 16 = 142 g. For phosphoric acid: 2 * (1 * 3 + 31 + 16 * 4) = 196 g.
From 142 g of phosphorus oxide, 196 g of acid will be formed, and from 21.3 g of phosphorus oxide, x g of acid will be formed.
We make the proportion: 142 / 21.3 = 196 / x;
We solve the equation and get: x = 21.3 * 196/142 = 29.4 g.
The resulting reaction solution of phosphoric acid contains 29.4 g.