Question

A reaction is first order in A and second order in B.

1. Write the differential rate equation. 
2. How is the rate affected on increasing the concentration of B three times? 
3. How is the rate affected when the concentrations of both A and B are doubled?

Answer 1

\((i)\) The differential rate equation will be

\(-\frac {d[R]}{dt }= k[A][B]^2\)

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\((ii)\) If the concentration of B is increased three times, then

\(-\frac {d[R]}{dt }= k[A][3B]^2\)

= \(9.  k[A][B]^2\)

Therefore, the rate of reaction will increase 9 times.

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\((iii)\) When the concentrations of both A and B are doubled,

\(-\frac {d[R]}{dt} = k[A][B]^2\)

= \(k[2A][2B]^2\)

= \(8. k[A][B]^2\)

Therefore, the rate of reaction will increase 8 times.