Chemical Kinetics

Chemistry Level 2

The rate of a reaction doubles when its temperature changes from 300 K to 310 K. What is the activation energy of such a reaction in kJ/mol?

Note: Use R = 8.314 J/K mol R=8.314\text{ J/K}\cdot\text{mol} and log 2 = 0.301. \log2=0.301.

(2013 mains)
48.6 53.6 58.5 60.5

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4 solutions

Chew-Seong Cheong
Feb 16, 2016

The rate of reaction k k is given by Arrhenius equation k = A e E a R T k = Ae^{-\frac{E_a}{RT}} , where A A is a frequency factor of the reaction, E a E_a the activation energy, R R the universal gas constant and T T temperature in K. Therefore we have:

k 2 k 1 = A e E a R T 1 A e E a R T 2 2 = e E a 8.314 ( 1 300 1 310 ) ln 2 = E a 8.314 ( 1 300 1 310 ) E a = 300 × 310 × 8.314 ln 2 310 300 = 53594.3 = 53.6 k J / m o l \begin{aligned} \frac{k_2}{k_1} & = \frac{Ae^{\frac{E_a}{RT_1}}}{Ae^{\frac{E_a}{RT_2}}} \\ 2 & = e^{\frac{E_a}{8.314}\left(\frac{1}{300}-\frac{1}{310}\right)} \\ \ln 2 & = \frac{E_a}{8.314}\left(\frac{1}{300}-\frac{1}{310}\right) \\ \Rightarrow E_a & = \frac{300\times 310 \times 8.314 \ln 2}{310-300} = 53594.3 = \boxed{53.6} \space kJ/mol \end{aligned}

Akhil Bansal
Jul 7, 2015

From arrhenius equation,logk2/k1= -Ea/2.303R (1/T2-1/T1) Given, k2/k1=2; T2=310K T1=300K On putting values, log2=-Ea/2.303*8.314(1/310-1/300) Ea=53598.6 J/mol=53.6 kJ/mol

Md Mehedi Hasan
Dec 12, 2017

l n k 1 k 2 = E a R ( 1 T 1 1 T 2 ) l n 1 2 = E a 8.314 ( 1 300 1 310 ) Calculating, E a = 53594.28 J / m o l 53.6 k J / m o l ln\dfrac{k_1}{k_2}=\dfrac{E_a}{R}\left( \dfrac{1}{T_1}-\dfrac{1}{T_2} \right)\\ ln\dfrac{1}{2}=\dfrac{E_a}{8.314}\left(\dfrac{1}{300}-\dfrac{1}{310}\right)\\ \text{Calculating, } E_a=53594.28J/mol\approx\boxed{53.6}kJ/mol

For proof, see this wiki Rate of chemical reaction

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