Question

What will be the change in volume when 100 mL $P{H}_3$ decomposed to solid phosphorus and $H_2$gas.

• A. Increase in 50 mL
• B. Decrease in 50 mL
• C. Increase in 150 mL
• D. Decrease in 200 mL

Answer 1

The correct option is A Increase in 50 mL

The equation for the decomposition is

$4P{H}_3\left(g\right)=P_4\left(s\right)+6H_2\left(g\right)$

when the temperature and pressure remain the same 4 ml of $P{H}_3$ will give 6 ml of $H_2$ (On applying Gay - Iussac's law)

Hence, 100 ml of $P{H}_3$ will yield 150 ml of $H_2$

Increase in volume = (150-100)ml = 50ml

(The volume of solid phosphorous is negligible)

There is a 50 mL increase in volume

Hence, the correct option is $A$