(a) A reaction is first order in A and second order in b.
(i) Write differential rate equation.
(ii) How is rate affected when concentration of B is tripled?
(iii) How is rate affected when concentration of both A and B is doubled ?
(b) What is molecularity of a reaction?
(a) (i) Differential rate equation
= rate = [A]1 [B]2
(ii) Rate r1 = K[A]1 [B]2 .....(1)
When concentration of B is increased three times then
Rate, r2 = K[A]1 [3B]2 ......(2)
Dividing equation (2) by (1), we get
r2 = 9 r1, i.e. rate increases by nine times.
(iii) When concentration of both A and B are doubled, then
r3 = K[2A]1 [2B]2 ......(3)
Dividing equation (3) by (1), we get
r3 = 8 r1,
Hence rate increases by eight times.
(b) The number of reacting species (atoms, ions or molecules) taking part in an elementary reaction is called Molecularity of a reaction.