Chemical Kinetics Part 1

Rate =k[A]x[B]y
When [B] is doubled, keeping [A] constant half-life of the reaction does not change.
For a first order reaction t1∕2=‌

0.693

K

i.e. for a first order reaction t1∕2 does not depend up on the concentration. Hence the reaction is first order with respect to B. Now when [A] is doubled, keeping [B] constant, the rate also doubles. Hence the reaction is first order with respect to A.
∴‌‌ Rate =k[A]1[B]1
Order of reaction =1+1=2
Now for a nth order reaction, unit of rate constant is (L)n−1(mol)1−n s−1 when n=2, unit of rate constant is Lmol−1 sec−1.