12th Standard Chemistry Chemical Kinetics English Medium Free Online Test One Mark Questions 2020 - 2021

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Questions:

Multiple Choice Question

19 x 1 = 19

The term A in Arrhenius equation is called as _____.

(a)

Probability factor

(b)

Activation energy

(c)

Collision factor

(d)

Frequency factor

During a chemical reaction, the concentration of reaction _____.

(a)

increases

(b)

decreases

(c)

remains constant

(d)

first increases and then decreases

What will be the rate constant of a order reaction if its half life is given to be 20 min?

(a)

13.86 min^-1

(b)

28.86 min^-1

(c)

3.47 x 10^-2 min^-1

(d)

None of these

The given reaction 2 FeCl₃ + SnCl₂ ⟶ 2FeCl₂ + SnCl₄ is an example of ______.

(a)

I order

(b)

II order

(c)

III order

(d)

None of these

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

(a)

Activation energy

(b)

Entropy

(c)

Internal energy

(d)

Enthalpy

Which order reaction obeys the expression \({ t }_{ \frac { 1 }{ 2 } }\alpha \frac { 1 }{ \left[ A \right] } ?\)

(a)

First

(b)

Second

(c)

Third

(d)

Zero

What would be the activation energy of a reaction when the temperature is increased from 27^oC to 37^oC?

(a)

534 kJ mol^-1

(b)

53.4 kJ mol^-1

(c)

5.34 kJ mol^-1

(d)

None of these

In pseudo-order reactions ______.

(a)

The actual order of reaction is different from that expected using rate law expression

(b)

The concentration of at least one reactant is taken in large excess.

(c)

The concentration of reactant taken in excess may be taken as constant

(d)

All of these

For a reaction, 2A + B ⟶ 3C, The rate of appearance of C at time 't' is 1.2 x 10^-4mol L^-1s^-1. Identify the rate of reaction.

(a)

4 x 10^-5mol L^-1s^-1

(b)

4.5 x 10^-1mol L^-1s^-1

(c)

3.6 x 10^-4mol L^-1s^-1

(d)

None of these

10.

2N₂O₅ ⟶ NO₂ + O₂, \(\frac { d\left[ { N }_{ 2 }{ O }_{ 5 } \right] }{ dt } \) = k₁[N₂O₅], \(\frac { d\left[ { NO }_{ 2 } \right] }{ dt } \)= k₂[N₂O₅] and \(\frac { d{ O }_{ 2 } }{ dt } \) = k ₃[N₂O₅], the relation between k₁, k₂ and k₃ is _____.

(a)

2k₁ = 4k₂ = k₃

(b)

k₁ = k₂= k₃

(c)

2k₁ = k₂ = 4k₃

(d)

2k₁ = k₂ = k₃

11.

This reaction follows first order kinetics. The rate constant at particular temperature is 2.303 x 10^-2 hour^-1. The initial concentration of cyclopropane is 0.25 M. What will be the concentration of cyclopropane after 1806 minutes? (log 2 = 0.3010)

(a)

0.125 M

(b)

0.215 M

(c)

0.25 x 2.303 M

(d)

0.05 M

12.

The correct difference between first and second order reactions is that________.

(a)

A first order reaction can be catalysed; a second order reaction cannot be catalysed.

(b)

The half life of a first order reaction does not depend on [A₀]; the half life of a second order reaction does depend on [A₀].

(c)

The rate of a first order reaction does not depend on reactant concentrations; the rate of a second order reaction does depend on reactant concentrations.

(d)

The rate of a first order reaction does depend on reactant concentrations; the rate of a second order reaction does not depend on reactant concentrations.

13.

If 75% of a first order reaction was completed in 60 minutes, 50% of the same reaction under the same conditions would be completed in_______.

(a)

20 minutes

(b)

30 minutes

(c)

35 minutes

(d)

75 minutes

14.

For the reaction \({ N }_{ 2 }{ O }_{ 5 }\left( g \right) \longrightarrow { 2NO }_{ 2 }\left( g \right) +\frac { 1 }{ 2 } { O }_{ 2 }\left( g \right) \) value of rate of disappearance of N₂O₅is given as 6.5 x 10^-2 mol L^-1s^-1. The rate of formation of NO₂ and O₂ is given respectively as_____.

(a)

(3.25 x 10^-2 mol L^-1s^-1) and (1.3 x 10^-2 mol L^-1s^-1)

(b)

(1.3 x 10^-2 mol L^-1s^-1) and (3.25 x 10^-2 mol L^-1s^-1)

(c)

(1.3 x 10^-1mol L^-1s^-1) and (3.25 x 10^-2 mol L^-1s^-1)

(d)

None of these

15.

What is the activation energy for a reaction if its rate doubles when the temperature is raised from 200K to 400K? (R = 8.314 JK^-1 mol^-1)

(a)

234.65 kJ mol^-1

(b)

434.65 kJ mol^-1

(c)

2.305 kJ mol^-1

(d)

334.65 J mol^-1

16.

Consider the following statements:
(i) increase in concentration of the reactant increases the rate of a zero order reaction.
(ii) rate constant k is equal to collision frequency A if E_a = 0
(iii) rate constant k is equal to collision frequency A if E_a = ∞
(iv) a plot of ln (k) vs T is a straight line.
(v) a plot of ln (k) vs \(\left( \frac { 1 }{ T } \right) \) is a straight line with a positive slope.
Correct statements are

(a)

(ii) only

(b)

(ii) and (iv)

(c)

(ii) and (v)

(d)

(i), (ii) and (v)

17.

For a reaction Rate = k[acetone]^3/2 then unit of rate constant and rate of reaction respectively is _______.

(a)

(mol L^-1 S^-1),(mol^1/2L^1/2S^-1)

(b)

(mol^-1/2L^1/2s^-1),(mol L^-1s^-1)

(c)

(mol^1/2L^1/2s^-1),(mol L^-1s^-1)

(d)

(mol L s^-1),(mol^1/2L^1/2s)

18.

Among the following graphs showing variation of rate constant with temperature (T) for a reaction, the one that exhibits Arrhenius behavior over the entire temperature range is _______.

(a)

(b)

(c)

(d)

both (b) and (c)

19.

For a first order reaction A ⟶ B the rate constant is x min⁻¹. If the initial concentration of A is 0.01M, the concentration of A after one hour is given by the expression.

(a)

001. e^−x

(b)

1 x 10^-2(1-e^-60x)

(c)

(1 x 10^-2)e^-60x

(d)

none of these

Assertion and reason

1 x 2 = 2

20.

Assertion: Rate of reaction doubles when the concentration of the reactant is doubles if it is a first order reaction.
Reason: Rate constant also doubles
Codes:
a) Both assertion and reason are true and reason is the correct explanation of assertion.
b) Both assertion and reason are true but reason is not the correct explanation of assertion.
c) Assertion is true but reason is false
d) Both assertion and reason are false.

(a)

Both assertion and reason are true and reason is the correct explanation of assertion.

(b)

Both assertion and reason are true but reason is not the correct explanation of assertion.

(c)

Assertion is true but reason is false

(d)

Both assertion and reason are false.

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Answers Key:

Multiple Choice Question

19 x 1 = 19

(d)
Frequency factor

(b)
decreases

(a)
Activation energy

(b)
Second

(d)
None of these

(d)
All of these

(a)
4 x 10^-5mol L^-1s^-1

10.

11.

\(k=\frac { 2.303 }{ t } log\frac { \left[ { A }_{ 0 } \right] }{ \left[ A \right] } \)
2.303 x 10^-2 hour^-1 = \(\frac { 2.303 }{ 1806 min } log\frac { \left[ { 0.25 }_{ } \right] }{ \left[ A \right] } \)
\(=\left(\frac{2.303 \times 10^{-2} hour^{-1 }\times 1806 min}{2.303}\right) = \log \left(\frac{0.25}{A}\right) \)
\(=\left(\frac{ 1806 \times 10 ^{-2}}{60}\right) = \log \left(\frac{0.25}{A}\right) \)
\(= 0.301 = \log \left(\frac{0.25}{A}\right) \)
\(=\log2 = \log \left(\frac{0.25}{A}\right) \)
\(2 = \log \left(\frac{0.25}{A}\right) \)
\([A] = \log \left(\frac{0.25}{2}\right) = 0.125 M\)

12.

\({ t }_{ 1/2 }=\frac { 0.6932 }{ k } \)
For a second order reaction
\(\mathrm{t}_{1 / 2}=\frac{2^{\mathrm{n}-1}-1}{(\mathrm{n}-1) \mathrm{k} \cdot\left[\mathrm{A}_{0}\right]^{\mathrm{n}-1}}\)
n = 2
\(\mathrm{t}_{1 / 2}=\frac{2^{\mathrm{2}-1}-1}{(\mathrm{n}-1) \mathrm{k} \cdot\left[\mathrm{A}_{0}\right]^{\mathrm{2}-1}}\)
\(\mathrm{t}_{1 / 2} =\frac{1}{ \mathrm{k}\left[\mathrm{A}_{0}\right]}\)

13.

t_75% = 2t_50%
t_50% = (t_75%/2) = (60/2) = 30 minutes

14.

Rate \(=\frac { d\left[ { N_2O_5 } \right] }{ dt } =\frac { 1 }{ 2 } =\frac { d\left[ { NO}_{ 2 } \right] }{ dt } =\frac { 2d\left[ { O }_{ 2 } \right] }{ dt } \)
Given that \(=\frac { d\left[ { N_2O_5 } \right] }{ dt } \) =6.5 x 10^-2 mol L^-1 s^-1
\(=\frac { d\left[ { NO}_{ 2 } \right] }{ dt }\) =2 x 6.5 x 10^-2= 1.3 x 10^-1mol L^-1 s^-1
\(=\frac { d\left[ { O}_{ 2 } \right] }{ dt }\)\(=\frac{6.5 \times 10^{-2}}{2}\) = 3.25 x 10^-2 mol L^-1s^-1

15.

T₁= 200 K ; k = k₁
T₂ =400 K ; k₁= k₂= 2k₁
log\(\frac {{ k }_{ 2 } }{ { k }_{ 1 } } =\frac { { E }_{ a } }{ 2.303R } \left[ \frac { { T }_{ 2 }-{ T }_{ 1 } }{ { T }_{ 1 }{ T }_{ 2 } } \right] \)
log \( [\frac {{2 k }_{ 1 } }{ { k }_{ 1 } }]\)
\(= \left[ \frac { E_{a} }{ 2.303\times 8.314 JK^{-1} mol^{-1} } \right] \)
\(= \left[ \frac { 400 k - 200K }{200 k \times 400 k } \right] \)
\(E_{a} = \frac{ 0.3010 \times 2.303 \times 8.314 JK^{-1}mol^{-1} \times 200K \times 400 K}{200 K}\)
E_a = 2305 J mol^-1
E_a = 2.305 kJ mol^-1

16.

(rate constant K is equal to collision frequency A if E_a = 0)
In zero order reactions, increase in the concentration of reactant does not alter the rate.
So statement (i) is wrong.
\(k=A{ e }^{ -\left( \frac { { E }_{ a } }{ RT } \right) }\)
if E_a = 0 so, statement (ii) is correct, and statement (iii) is wrong
k = Ae⁰
k = A
In k = In A - \({ \left( \frac { { E }_{ a } }{ R } \right) }\) \(\left( \frac { 1 }{ T } \right) \)
This equation is of the form of a straight line y = mx+c
A plot of In k Vs \(\left( \frac { 1 }{ T } \right) \) gives a straight line with a negative slope
So statement (iv) and (v) are wrong.

17.

Rate = k[A]ⁿ
Rate = \(\frac{-\mathrm{d}[\mathrm{A}]}{\mathrm{dt}}\)
unit of rate = \(\frac{mol L^{-1}}{s}\)=mol L^-1/s^-1
unit of rate constant
\(=\frac{ (mol{ L }^{ -1 }{ S }^{ -1 }) }{ ({ mol }{ L }^{ -1 })^n } \)
= mol^1-nL^n-1s^-1
in the case
rate = k [Acetone]^3/2
n = 3/2
= mol^1-(3/2)L^(3/2)-1s^-1
(mol^-(1/2)L^(1/2)s^-1).

18.

\(k=A{ e }^{ -\left( \frac { { E }_{ a } }{ RT } \right) }\)
In k = In A - \({ \left( \frac { { E }_{ a } }{ R } \right) }\) \(\left( \frac { 1 }{ T } \right) \)
This equation is of the form of a straight line y = mx+c
A plot of In k Vs \(\left( \frac { 1 }{ T } \right) \) gives a straight line with a negative slope.

19.

\(k=\frac { 2.303 }{ t } log\frac { \left[ { A }_{ 0 } \right] }{ \left[ A \right] } \)
\(k=\frac { 1 }{ t } ln \frac { \left[ { A }_{ 0 } \right] }{ \left[ A \right] } \)
\(e^{kt}=\frac { \left[ { A }_{ 0 } \right] }{ \left[ A \right] }\)
[A] = [A₀] e^kt
In this case
k = x min^-1 and [A₀] = 0.01 M = 1 x 10^-2M
t = 1 hour = 60 min
[A] = (1 x 10^-2)e^-60x