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Question:

In a homogeneous reaction A → B + C + D, the initial pressure was P0 and after time t it was P. Expression for rate constant k in terms of P0, P and t will be:

k=2.303tlog2P03P0−P

k=2.303tlog2P0P0−P

k=2.303tlog3P0−P2P0

k=2.303tlog2P03P0−P

Solution:

A → B + C + D
Initial a 0 0 0
After time t a-x x x x
It is given that at time t, a = P0.. (i)
a - x + x + x + x = P (ii)
From (i) P0 + 2x = P or x = P - P0 / 2
From rate equation k = 2.303/t log a / a - x
k = 2.303/t log 2P0 / 3P0 - P