1. Assume that the rate law for a reaction is rate = k[A][B]^2 a) what is the ov
ID: 945551 • Letter: 1
Question
1. Assume that the rate law for a reaction is rate = k[A][B]^2
a) what is the overall order of the reaction?
b) if the concentration of both A and B are doubled, how will this affect the rate of the reaction?
c) how will doubling the concentration of A, while the concentration of B is kept constant, affect the value of k (assume that temperature does not change)? how is the rate affected?
2. It is found for the reaction 2A + B ---> C that doubling the concentration of either A or B while maintaining the other concentration constant quadruples the reaction rate. Write a rate law for the reaction.
Explanation / Answer
Answer.(a) given rate law is r =k[A][B]2-------------(1) from the given rate law order of the reaction w.r.to A is one,and the order of the reaction w.r.to B is two.so ,the overall order of the reaction is three. order=3.
(b) if the concentration of bothA and B are the doubled,let the rate would be r1. r1=k[2A][2B]2=8xk[A][B]2=8x r.so the rate becomes 8 times the initial rate.
(c)if the concentration of A is doubled,let rate would be r2. r2 =k[2A][B]2 =2xk[A][B]2=2xr. so, the rate becomes double..
'k' value does not change because temperature is constant.
2.Answer.given reaction is 2A+B-------->C let' a' be the order of the reaction w.r.to A,ans 'b' be the order of reaction w.r.to B.then rate law is r=k1[A]a[B]b----(2)
case i)if the concentration of A is doubled let the rate would be r3,becomes quadrapled.,then r3=k1[2A]a[B]b=2axk1[A]a[B]b=r/4
2axr=r/4 , on solving a=-2
caseii) if the concentration of B is doubled let the rate would be r4,becomes quadrapled.,then r4=k1[A]a[2B]b=2bxk1[A]a[B]b=r/4
2bxr=r/4 , on solving b=-2
rate law for the above reaction is r=k1[A]-2[B]-2 .
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