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.

EASY

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A collision between reactant molecules must occur with a certain minimum energy before it is effective in yielding product molecules. This minimum energy is called activation energy $E_{a}$ ⋅ Larger the value of activation energy, smaller the value of rate constant $k$ . Larger is the value of activation energy, greater is the effect of temperature rise on rate constant $k$ .

$E_{f}$ = Activation energy of forward reaction $E_{b}$ = Activation energy of backward reaction = $ΔH = E_{f} - E_{b}$

$E_{t} =$ Threshold energy
If a reaction $A + B \to C$ is exothermic to the extent of $30 kJ$ ${mol}^{- 1}$ and the forward reaction has an activation energy of $249 kJ$ ${mol}^{- 1}$ the activation energy for reverse reaction in $kJ$ ${mol}^{- 1}$ is

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Important Questions on Chemical Kinetics

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Mechanism of a Chemical 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>Mechanism of a Chemical 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>Mechanism of a Chemical 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.

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Mechanism of a Chemical Reaction

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

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Mechanism of a Chemical Reaction

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

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Mechanism of a Chemical 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>Mechanism of a Chemical Reaction

Which among the following equations represents Arrhenius equation?

HARD

Chemistry>Physical Chemistry>Chemical Kinetics>Mechanism of a Chemical Reaction

For the following reactions

A \overset{700 K}{\to} Product

A \overset{500 K}{\underset{catalyst}{\to}} Product

It was found that the

E_{a}

is decreased by

30 K J / m o l

in the presence of catalyst. If the rate remains unchanged, the activation energy for catalysed reaction is (Assume pre-exponential factor is same)

MEDIUM

Chemistry>Physical Chemistry>Chemical Kinetics>Mechanism of a Chemical 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}

]

EASY

Chemistry>Physical Chemistry>Chemical Kinetics>Mechanism of a Chemical 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>Mechanism of a Chemical 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})

HARD

Chemistry>Physical Chemistry>Chemical Kinetics>Mechanism of a Chemical 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)