EASY

Earn 100

How to calculate activation energy if the value of rate constant given at two different temperatures.

Important Questions on Chemical Kinetics

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

For a reaction, consider the plot of $l n k$ versus $1 / T$ given in the figure. If the rate constant of this reaction at $400 K$ is $10^{- 5} s^{- 1}$ , then the rate constant at $500 K$ is:

Question Image

HARD

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

Consider the following reversible reaction:

A (g) + B (g) ⇌ AB (g)

The activation energy of the backward reaction exceeds that of the forward reaction by

2 RT

(in

{mol}^{- 1}

). If the pre-exponential factor of the forward reaction is

4

times that of the reverse reaction, the absolute value of

∆ G^{⊝} (in J {mol}^{- 1})

for the reaction at

300 K

is ____.

(Given;

\ln (2) = 0 .7, = 2500 J {mol}^{- 1} at 300 K

and

G

is the Gibbs energy)

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The rate of a certain biochemical reaction at physiological temperature

(T)

occurs

10^{6}

times faster with enzyme than without. The change in the activation energy upon adding enzyme is:

HARD

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The activation energy of a reaction can be determined from the slope of which of the following graphs?

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The rate of a reaction quadruples when the temperature changes from

300

310 K

. The activation energy of this reaction is:

(Assume Activation energy and pre-exponential factor are independent of temperature;

\ln (2) = 0.693; R = 8.314 J {mol}^{- 1} K^{- 1}

)

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

Which is a wrong statement?

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The activation energy of a reaction is zero. Its rate constant at 280 K is

1.6 \times 10^{- 6} s^{- 1},

the rate constant at 300 K is

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The rate constant is doubled when temperature increases from

27 ° C

37 ° C .

Activation energy in

kJ

is:

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The Arrhenius plots of two reactions, I and II are shown graphically-

Question Image

The graph suggests that-

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The rate constant of a chemical reaction at a very high temperature will approach

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The number of molecules with energy greater than the threshold energy for a reaction increases five fold by a rise of temperature from

27^{o} C

42^{o} C

. Its energy of activation in

J / mol

is _________ (Take

\ln 5 = 1.6094; R = 8.314 J {mol}^{- 1}

)

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

Two reactions

A_{1}

and

A_{2}

have identical pre-exponential factors. The activation energy of

A_{1}

is more than

A_{2}

10 kJ {mol}^{- 1}

. If

k_{1}

and

k_{2}

are the rate constants for reactions

A_{1}

and

A_{2}

, respectively at

300 K

, then

\ln (\frac{k_{2}}{k_{1}})

is equal to

(R = 8 .314 J {mol}^{- 1} K^{- 1})

HARD

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of Reaction Rates

The rate constant $(k)$ of a reaction is measured at different temperature $(T)$ , and the data are plotted in the given figure. the activation energy of the reaction in ${kJmol}^{- 1}$ is : $(R$ is gas constant)

Question Image