Phosphorus burns in oxygen according to the equation P4 + 502 → P4O10. How many litres of oxygen will be required at S.T.P for complete oxidation of 12.4g of phosphorus? [P = 31,O = 16 and molar volume of a gas at S.T.P = 22.4 litres]

A.

5. 20

B.

11. 20

C.

2. 24

D.

20. 20

E.

6. 20

Correct answer is B

P4 + 502 → P4O10

for the complete combustion of 124 grammes of phosphorus we need

5 x 22.4 litres of O2

for 12.4 gms of P4 we need

\(\frac{5 \times 22.4}{124} \times \frac{12.4}{1}\)

\(\frac{22.4}{2}\) = 11.2 litres