Calculate the mass of phosphorus (V) oxide required to obtain 3.92 g of phosphoric acid.

univerkov | March 2, 2021 | education

Given:
m (H3PO4) = 3.92 g

To find:
m (P2O5) -?

Decision:
1) P2O5 + 3H2O => 2H3PO4;
2) n (H3PO4) = m (H3PO4) / Mr (H3PO4) = 3.92 / 98 = 0.04 mol;
3) n (P2O5) = n (H3PO4) / 2 = 0.04 / 2 = 0.02 mol;
4) m (P2O5) = n (P2O5) * Mr (P2O5) = 0.02 * 142 = 2.84 g.

Answer: The mass of P2O5 is 2.84 g.

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