Question

Concentrated nitric acid oxidizes phosphorous to phosphoric acid according to the following equation :
P + 5HNO₃ → H₃PO₄ + H₂O + 5NO₂
What will be the volume of steam at the same time measured at 760mm of Hg pressure and 273°C? [H=1, N=14, O=16, P=31]

Answer 1

Given equation is :
P + 5HNO₃ → H₃PO₄ + H₂O + 5NO₂

Moles of steam formed from 31g phosphorus = 1 mol
moles of steam from 6.2g phosphorus = 1mol x 6.2g / 31g
= 0.2 mol.
volume of steam produced at S.T.P = (0.2 mol) x (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 x 2 = 8.96 litres.