(a) Show graphically how the rate of first order reaction vary with only one reactant depends concentration of reactant.
(b) Give one example of first order reaction.
above graph show that by increasing the concentration of reactant the rate of reaction also increase.
(b) Example of first order reaction is Hydrogenation of ethene is an example of first order reaction.
C2H4(g) + H2 (g) → C2H6(g)
Rate = k [C2H4]
This reaction follows second order kinetics.
So that, the rate equation for this reaction will
Rate, R = k[X]2 .............(1)
Let initial concentration is x mol L−1,
Plug the value in equation (1)
Rate, R1 = k .(a)2
Given that concentration is increasing by 3 times so new concentration will 3a mol L−1
Plug the value in equation (1) we get
Rate, R2 = k (3a)2
We have already get that R1 = ka2 plus this value we get
R2 = 9 R1
So that, the rate of formation will increase by 9 times.
Rate = k[A]2
If concentration of X is increased to three times,
Rate = k[3A]2
or Rate = 9 k A2
Thus, rate will increase 9 times.