Consider the given plot of enthalpy of the following reaction between A and B . A + B → C + D . Identify the incorrect statement.

Activation enthalpy to form C is 5 k J m o l - 1 less than that to form D .

Formation of A and B from C has highest enthalpy of activation.

D is kinetically stable product.

C is the thermodynamically stable product.

For a first order reaction A → P , the temperature T dependent rate constant k was found to follow the equation logk =- 2000 1 T + 6 .0 . The pre-exponential factor A and the activation energy E a , respectively, are

1.0 × 10 6 s - 1 and 38.3 kJ mol - 1

1.0 × 10 6 s - 1 and 9.2 kJ mol - 1

1.0 × 10 6 s - 1 and 16.6 kJ mol - 1

EASY

Earn 100

At what conditions exponential factor is zero for a reaction

(i) At infinite temperature

(ii) For free radical combination

(iii) When energy of activation $=$ Threshold energy

50% studentsanswered this correctly

Important Questions on Chemical Kinetics

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

Slope of the straight line obtained by plotting

{log}_{10} k

against

\frac{1}{T}

represents which term?

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

The enthalpy

(H)

of an elementary exothermic reaction

A ⇌ B

is schematically plotted against the reaction coordinate. The plots in the presence and absence of a catalyst are shown in dashed and solid lines, respectively. Identify the correct plot for the reaction.

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

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})

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

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 the Rate of a Reaction

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

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

The rate of a reaction A doubles on increasing the temperature from

300 to 310 K

. By how much, the temperature of reaction B should be increased from

300 K

so that rate doubles if activation energy of the reaction B is twice to that of reaction A.

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

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 the Rate of a Reaction

Consider the given plot of enthalpy of the following reaction between

A

and

B .

A + B \to C + D .

Identify the incorrect statement.
Question Image

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

The rate of a reaction doubles when its temperature changes from

300 K to 310 K

. Activation energy of such a reaction will be:

(R = {8.314 JK}^{-1} {mol}^{-1} and log 2 = 0.301)

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

For the equilibrium,

A (g) ⇌ B (g), ∆ H is - 40 kJ / mol

. If the ratio of the activation energies of the forward

(E_{f})

and reverse

(E_{b})

reactions is

\frac{2}{3}

then:

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

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 the Rate of a Reaction

The addition of a catalyst during a chemical reaction alters which of the following quantities?

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

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

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

Which among the following equations represents Arrhenius equation?

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

For the reaction of

H_{2}

with

I_{2}

, the rate constant is

2.5 \times 10^{- 4} d m^{3} m o l^{- 1} s^{- 1}

327^{o} C

and

1.0 d m^{3} m o l - 1 s^{- 1}

527 ° C

. The activation energy for the reaction, in

k J m o l - 1

is:

(R = 8.314 J K^{- 1} m o l^{- 1})

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

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:

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

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 the Rate of a Reaction

A reaction has an activation energy of

209 k J m o l^{- 1}

. The rate increases

10

-fold when the temperature is increased from

27^{o} C

X^{o} C

. The temperature

X

is closest to

[Gas constant,

R = 8.314 J m o l^{- 1} K^{- 1}

]

HARD

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

Consider the given plots for a reaction obeying Arrhenius equation $(0 ° C < T < 300 ° C) :$ ( $K$ and $E_{a}$ are rate constant and activation energy, respectively )

(I)

Question Image

(II)

Question Image

HARD

Chemistry>Physical Chemistry>Chemical Kinetics>Temperature Dependence of the Rate of a Reaction

For a first order reaction

A \to P,

the temperature

(T)

dependent rate constant

(k)

was found to follow the equation

logk =- (2000) \frac{1}{T} + 6 .0 .

The pre-exponential factor A and the activation energy

E_{a},

respectively, are

At what conditions exponential factor is zero for a reaction (i) At infinite temperature (ii) For free radical combination (iii) When energy of activation=Threshold energy

Important Questions on Chemical Kinetics

Learn and Prepare for any exam you want !

At what conditions exponential factor is zero for a reaction

(i) At infinite temperature

(ii) For free radical combination

(iii) When energy of activation $=$ Threshold energy