For the reaction, 2A+B→A2B the rate =k[A][B]2 with k=2.0×10−6 mol−2 L−2 s−1. Calculate the initial rate of reaction when [A]=0.1 mol L−1,[B]=0.2 mol L−1. Calculate the rate of reaction after [A] is reduced to 0.06 mol L−1.
(i) Case I: Rate =k[A][B]2
=(2.0×10−6 mol−2 L−2 s−1)×(0.1 mol L−1)×(0.2 mol L−1)2
=8.0×10−9 mol L−1 s−1
(ii) Case II: Concentration of A at a particular time =0.06 mol L−1
Amount of A reacted =(0.1−0.06)=0.04 mol L−1
Amount of B reacted =12×0.04 mol L−1=0.02 mol L−1
Concentration of B at a particular time
=(0.2−0.02) mol L−1=0.18 mol L−1
Rate =k[A][B]2
=(2.0×10−6 mol−2 L2 s−1)×(0.06 mol L−1)×(0.18 mol L−1)2
=3.89×10−9 mol L−1 s−1