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 volume of steam produced at the same time if measured at 760 mm Hg pressure and 273°C.

Answer 1

Moles of steam formed from 31 g phosphorus = 1 mol

Moles of stream formed from 6.2g phosphorus = `(1  "mol")/(31  "g")`

= 0.2 mol

Volume of steam produced at S.T.P. = (0.2 mol) × (22.4 L/mol)

= 4.48 litre

Since the pressure (760 mm) remains constant, but the temperature (273 + 273) = 546 is doubled, the volume of the steam also gets doubled.

∴ Volume of steam produced at 760 mm Hg and 273°C = 4.48 × 2

= 8.96 litre