Question

# The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the

A
rate is independent of the surface coverage
B
rate of decomposition is very slow
C
rate is proportional to the surface coverage
D
rate is inversely proportional to the surface coverage

Solution

## The correct option is A rate is proportional to the surface coverageThe decomposition of PH3 on tungsten at low pressure is a first order reaction because rate is proportional to the surface coverage and at low pressure, the surface area coverage is proportional to the partial pressure of PH₃. While as higher and higher pressures are reached, a certain increase in the pressure doesn't lead to an increase in the rate by the same factor because a correspondingly equivalent increase in surface coverage is not achieved.

Suggest corrections