Question

Concentrated nitric acid oxidizes phosphorus to phosphoric acid according to the following equation:

\[\ce{P + 5HNO3 -> H3PO4 + 5NO2 + H2O}\]

If 6.2 g of phosphorus was used in the reaction, calculate the number of moles of phosphorus taken and mass of phosphoric acid formed.

Answer 1

\[\ce{\underset{[Steam 1 mole]}{P + 5HNO3} -> H3PO4 + H2O + 5NO2}\]

1 mole of phosphorus atom = 31 g of phosphorus

31 g of P = 1 mole of P

∴ 6.2 g of P = `(6.2 xx 1)/31`

= 0.2 mole of P

Also, 31 g of phosphorus or 1 mole of phosphorus produces H₃PO₄

= (3 × 1) + 31 + (4 × 16)

= 98 g of H₃PO₄

∴ 0.2 mole of P produces = 98 × 0.2

= 19.6 g of H₃PO₄