Question

(a) What is rate of reaction? Write two factors that affect the rate of reaction.

(b) The rate constant of a first order reaction increases from $4\times {10}^{-2}$ to $8\times {10}^{-2}$ when the temperature changes from ${27}^{\circ }C$ to ${37}^{\circ }C$.
Calculate the energy of activation $\left(E_a\right)$. (log 2 =0.301, log 3 =0.4771, log 4 =0.6021)

Answer 1

(a) Rate of a reaction is defined as the change in the concentration of any one of the reactants or products per unit time.

TWO factors affecting rate of a reaction are :

(i) Concentration of reactants
(ii) Temperature.

$\left(b\right)T_1={27}^{\circ }C+273=300K$

$T_2={37}^{\circ }C+273=310K$

$k_1=4\times {10}^{-2}se{c}^{-1}{k}_2=8\times {10}^{-2}se{c}^{-1}$

$log\frac{k_2}{k_1}=\frac{E_a}{2.303R}\left(\frac{T_2-T_1}{T_2\times T_1}\right)$

$log\frac{8\times {10}^{-2}}{4\times {10}^{-2}}=\frac{E_a}{2.303\times 8.314}\times \frac{310-300}{310\times 300}$

$log2=\frac{E_a}{19.147142}\times \frac{10}{93000}$

$0.3010=\frac{E_a}{178068.4}$

or $E_a=178068.4\times 0.3010$

$=53598.6Jmo{l}^{-1}$

$=53.6kJmo{l}^{-1}$