# NEET Questions Solved

NEET - 2016

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

(a) rate is proportional to the surface coverage

(b) rate is inversely proportional to the surface coverage

(c) rate is independent of the surface coverage

(d) rate of decomposition is very slow

Concept Videos :-

#8 | Problems on 1st Order Reaction (Type 1)
#9 | Problems on 1st Order Reaction (Type 2)
#10 | Problems on 1st Order Reaction (Type 3)
#12 | Problems on 1st Order Reaction (Type 5)

Concept Questions :-

First Order Reaction Kinetics

(a) PH3 $\stackrel{\mathrm{w}}{\to }$P +3/2. H2

This is an example of surface catalysed unimolecular decomposition.

For the above reaction, rate is given as

Rate = k$\mathrm{\alpha \rho }$/1+$\mathrm{\alpha \rho }$

where, $\mathrm{\rho }$ = partial pressure of absorbing substrate.

At low pressure, $\mathrm{\alpha \rho }$

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