Question Set A

cbse 12th Standard Chemistry Chemical Kinetics Model Questions Papers Study Material - QB365

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Questions:

Multiple Choice Question

90 x 1 = 90

For the reaction A + 2B \(\rightarrow\) C + D. The order of the reaction is

(a)

1 with respect to A

(b)

2 with respect to B

(c)

can't be predicted as order is determined experimentally.

(d)

The rate of a reaction increases sixteen times when the concentration of the reactant increases four times.The order of the reaction is

(a)

2.5

(b)

2.0

(c)

1.5

(d)

0.5

The non-stoichiometric reaction:
2A + B \(\rightarrow\) C+D

Initial conc A	Initial conc of B	Initial rate (Mol L^-1)
0.1 M	0.1 M	1.2 x 10^{- 3}
0.1 M	0.2M	1.2 x 10^{- 3}
0.2 M	0.1 M	2.4 x 10^{- 3}

The rate law for formation of c is

(a)

\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}]\)

(b)

\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}][\mathrm{B}]\)

(c)

\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}]^{2}[\mathrm{~B}]^{1}\)

(d)

\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}][\mathrm{B}]^{2}\)

In Arrhenius plot of Ink Vs \(\frac{1}{\mathrm{~T}}\) is a linear plot obtained with slope of -2 x 10⁴ k. Ea of reaction in kJ mol ^-1.

(a)

(b)

166

(c)

249

(d)

332 kJ mol ^-1

The rate of chemical reaction double for every 10° rise of temperature. If the temperature is raised by 50°, the rate of reaction will increase by

(a)

10 times

(b)

24 times

(c)

32 times

(d)

64 times

In the first order reaction the concentration of reactant decreases from 0.6 M to 0.3 M in 30 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M:

(a)

60 min

(b)

30 min

(c)

15 min

(d)

50 min

For a reaction taking place in three steps, the overall rate constant k \(=\frac{k_{1} k_{2}}{k_{3}}\) If Ea₁, Ea₂ and Ea₃ are the 40, 50 and 60 kJ mol^-1, the overall E_a is

(a)

(b)

(c)

(d)

If the initial concentration of reactant is doubled, t_1/2 is also doubled, the order of reaction is

(a)

zero

(b)

(c)

(d)

The rate of first order reaction is 0.04 mol L^-1 s^-1 at 10 sec. and 0.03 mol L^-1 at 20 seconds after initiation of the reaction. t_1/2of reaction is

(a)

44.1 s

(b)

54.1 s

(c)

24.1 s

(d)

34.1 s

10.

A first order reaction has specific reaction rate 10^{- 2}s^-1 . How much time it will take for 20g of reactant to reduce to 5g?

(a)

138.6 s

(b)

346.5 s

(c)

693.0 s

(d)

238.6 s

11.

Which of the following is affected by catalyst?

(a)

\(\triangle\)H

(b)

\(\triangle\)S

(c)

\(\triangle\)G

(d)

E_a

12.

The half life period of first order reaction is 1386 seconds. The specific rate constant ofthe reaction is

(a)

0.5 x 10^{- 2} s^-1

(b)

0.5 x 10^{- 3} s^-1

(c)

5.0 x 10^{- 2} s^-1

(d)

5.0 x 10^-3 S^-1

13.

Consider the following plot between In k and 1/T,

In this plot, the intercept and slope respectively are

(a)

\(-\frac{E_{a}}{R} ; \ln A\)

(b)

\( \ln A ;-\frac{E_{\alpha}}{R}\)

(c)

\(\frac{E_{a}}{R} ;-\ln A\)

(d)

\( \frac{E_{a}}{R} ; A\)

14.

According to Arrhenius equation rate constant k is equal to A e.^-Ea/RT Which of the following options represents the graph of In k vs 1/T

(a)

(b)

(c)

(d)

15.

Arrhenius equation may not be represented as

(a)

\( \ln \frac{A}{k}=\frac{E_{a}}{R T}\)

(b)

\(K=Ae^-Ea/RT\)

(c)

\(\log A=\log k+\frac{E_{\alpha}}{2303 R T}\)

(d)

\(\log k-\left(\frac{E_{a}}{R T}\right)=A\)

16.

When one reactant is present in large excess in a chemical reaction between two substances, then the reaction is known as

(a)

first order reaction

(b)

second order reaction

(c)

zero order reaction

(d)

pseudo first order reaction

17.

Expression for the half-life of zero order reaction is given as

(a)

\( t_{1 / 2}=\frac{[R]}{2 k}\)

(b)

\(t_{1 / 2}=\frac{[R]_{0}}{2 k}\)

(c)

\(t_{1 / 2}=\frac{0.693}{k}\)

(d)

\(t_{1 / 2}=\frac{0.301}{k}\)

18.

For the reaction,

half-life does not depend on the concentration of the reactant. After 10 min, volume of N₂gas is 20 L and after the completion of reaction, it is 100 L. Hence, rate constant is

(a)

\(\frac{2.303}{10}\) log 5 min^-1

(b)

\(\frac{2.303}{10}\) log 10 min^-1

(c)

\(\frac{2.303}{10}\) log 10 min^-1

(d)

\(\frac{2.303}{10}\) log 20 min^-1

19.

Equation for rate constant of a first order reaction is

(a)

\( k=\frac{2.303}{t} \log _{10} \frac{a}{(a-x)}\)

(b)

\(k=\frac{4 \cdot 306}{t} \log _{10} \frac{a}{(a-x)}\)

(c)

\( k=\frac{2.303}{t^{2}} \log _{10} \frac{a}{(a-x)}\)

(d)

\( k=\frac{10}{t} \log _{10} \frac{a}{(a-x)}\)

20.

Four reactions are given below. Which one of them is of zero order?

(a)

\(\mathrm{PCL}_{5} \longrightarrow \mathrm{PCl}_{3}+\mathrm{Cl}_{2}\\ \)

(b)

\( 2 \mathrm{FeCl}_{\mathrm{s}}+\mathrm{SnCl}_{2} \longrightarrow 2 \mathrm{FeCl}_{2}+\mathrm{SnCl}_{4}\\ \)

(c)

\( \mathrm{H}_{2}+\mathrm{Cl}_{2} \longrightarrow 2 \mathrm{HCl}\\ \)

(d)

\( \mathrm{N}_{2} \mathrm{O}_{5} \longrightarrow 2 \mathrm{NO}_{2}+\frac{1}{2} \mathrm{O}_{2}\\\)

21.

For the given rate expression = k[A]^3/2[B]^-1, the overall-order of a reaction is

(a)

zero

(b)

half

(c)

one

(d)

two

22.

Consider the data given below for a hypothetical reactions, M ⟶ N

Time(s)	Rate of reaction (mol L^-1 s^-1)
0	4.20 x 10^-4
10	4.20 x 10^-4
20	4.20 x 10^-4
30	4.20 x 10^-4
40	4.18 x 10^-4

For the above data, the order of reaction is

(a)

one

(b)

two

(c)

three

(d)

zero

23.

For which of the following, the units of rate constant and rate of the reaction are same?

(a)

Zero order reaction

(b)

First order reaction

(c)

Second order reaction

(d)

Third order reaction

24.

Find the order of the reaction whose rate constant is 2.5 x 10^-2 min^-1

(a)

zero

(b)

three

(c)

two

(d)

one

25.

During a chemical reaction with increase in temperature, rate of a reaction

(a)

decreases

(b)

increases

(c)

remains constant

(d)

show irregular trends

26.

In a reaction, 2x ⟶ y, the concentration of x decreases from 3.0 M to 1.5 Min 4 min. The rate of the reaction is

(a)

0.187 M min^-1

(b)

1.87 M min^-1

(c)

3.75 x 10^-1M min^-1

(d)

0.75 M min^-1

27.

Rate of which of the following reactions can be determined easily?

(a)

Rusting of iron in the presence of air and moisture

(b)

Hydrolysis of starch

(c)

Reaction of silver nitrate with sodium chloride

(d)

All of the above

28.

For the first order reaction
2 N₂O₅ (g) \(\longrightarrow\) 4 NO₂ (g) + O₂ (g)

(a)

the concentration of the reactant decreases exponentially with time

(b)

the half-life of the reaction decreses with increases temperature

(c)

the half-life of the reaction depends on the initial concentration of the reactant

(d)

the reaction proceeds to 99/6% completion in eight half-duration

29.

A catalyst

(a)

increases the average kinetic energy of the reacting molecules.

(b)

decreases the activation energy

(c)

alters the reaction mechanism

(d)

increaes the frequency of collision of the reacting species

30.

The initial rate hydrolysis of methyl acetate (1 M) by a week acid (HA, 1 M) is 1/100th of that of a strong acid (HX, 1 M) at 25^oC. The k_a of HA is

(a)

1 \(\times 10 ^{-4}\)

(b)

1\(\times 10 ^{-5}\)

(c)

1\(\times 10 ^{-6}\)

(d)

1\(\times 10 ^{-3}\)

31.

The oxidation of a certain metal is found to obey the equation A2 = \(\alpha t + \beta\) , where A is the thickness of the oxide film at time t , \(\alpha\) and \(\beta\) are constants. The order of this reaction is

(a)

(b)

(c)

-1

(d)

32.

Consider the following statements :
(i) increase in concentration of reactant increses the rate of zero order reaction
(ii) rate constant k is equal to collision frequency A is E_a = 0
(iii) rate constant k is equal to collision frequency A if E_a = \(\infty \).
(iv) In k vs T is a straight line
(v) in k vs 1/T is a straight line.
correct statement are :

(a)

(i) and (iv)

(b)

(ii) and (v)

(c)

(iii) and (iv)

(d)

(ii) and (iii)

33.

One mole of N₂O₄ gas at 300 K is kept in a closed container at 1 atm. It is heated to 600 K when 20% by mass of N₂O₄ decomposes to NO₂(g). The resultant pressure in the container would be

(a)

1.2 atm

(b)

2.4 atm

(c)

2.0 atm

(d)

1.0 atm

34.

Which one of the following is not correct ?

(a)

Every biomolecular collision does not result into a chemical reaction.

(b)

collosion theory is not applicable to unimolecular reaction

(c)

according to collision frequency, k = PZ _AB e^-E/RT where Z_AB is collision frequency and P is steric factor

(d)

Collision theory assumes molecules to be hard speres

35.

The rate constants k₁and k₂for two different reactions are 10¹⁶. e^-2000/T and 1015. e^-1000/T respectively. The temperature at which k₁ = k₂ is

(a)

1000 K

(b)

\(\frac {2000}{2.303}K\)

(c)

2000 K

(d)

\(\frac {1000}{2.303}K\)

36.

For a reaction taking place in three steps, the rate constants are k1,k2 and k3. The overall rate constant is \(k = \frac {k_1k_2}{k_3}\). The overall energy of activation in kJ mol^-1 is

(a)

(b)

150

(c)

(d)

37.

For an endothermic reaction, where \(\triangle H\) represents the enthalpy of the reaction in kJ/mol. The minimum value for the energy of activation will be

(a)

less than \(\triangle H\)

(b)

zero

(c)

more than \(\triangle H\)

(d)

equal to \(\triangle H\)

38.

H2O2 is formed in the upper atmosphere through the following mechanism
H2O + (O) \(\longrightarrow\) 2OH \(\longrightarrow\) H₂O₂
The overall enthalpy change and activation energy for the forward reaction are 72 kJ mol^-1and 77 kJ mol^-1respectively. The activation energy for the decomposition of H₂O₂ to give back H₂O and (O) will be

(a)

5 kJ mol^-1

(b)

-5 kJ mol^-1

(c)

149 kJ mol^-1

(d)

-149 kJ mol^-1

39.

In the presence of a catalyst, the activation energy of a reaction is lowered by 2kcal at 27^oC. The rate of reaction will increase by

(a)

2 times

(b)

14 times

(c)

28 times

(d)

20 times

40.

The rate of a reaction doubles when its temperature changes from 300 K to 310 K activation energy of such a reaction will be

(a)

60.5 kJ mol^-1

(b)

53.6 kJ mol^-1

(c)

48.6 kJ mol^-1

(d)

58.5 kJ mol^-1

41.

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

(a)

In k vs \(\frac {1}{T}\)

(b)

\(\frac {T}{In k} vs \frac {1}{T}\)

(c)

In k vs T

(d)

\(\frac {In k} {T}\) vs T

42.

Number of natural life times (t_av) required for a first reaction to complete 99.9% is

(a)

6.93

(b)

2.31

(c)

9.2

(d)

infinite

43.

In the study of inversion of surcose in presence of readings at times r0 , r1 and \({ r }_{ \infty }\) represent the polarimetric readings at times 0, t and \( \infty \) respectively, then at the 50% inversion, which of the following relationship will hold good ?

(a)

\({ r }_{t }={ r }_{0 }+{ r }_{ \infty }\)

(b)

\({ r }_{t }\frac {1}{2}({ r }_{0 }+{ r }_{ \infty })\)

(c)

\({ r }_{t }={ r }_{0 }-{ r }_{ \infty }\)

(d)

\({ r }_{t }\frac {1}{2}({ r }_{0 }-{ r }_{ \infty })\)

44.

For the elementary reaction M \(\longrightarrow\) N, the rate of disappearance of M increses by a factor of 8 upon doubling the concentration of M. The order of reaction with respect to M is

(a)

(b)

(c)

(d)

45.

Under the same reaction conditions, initial concentration of 1.386 mol dm^-3 of a substance becomes half in 40 seconds and 20 seconds through first order and zero kinetices respectively. Ratio (k₁/k₀) of the rate constants for first order (k₁) and zero order (k₀) of the reactions is

(a)

0.5 mol^-1dm³

(b)

1.0 mol^-1 dm^-3

(c)

1.5 mol^-1 dm^-3

(d)

2.0 mol^-1 dm³

46.

For a second order reaction, 2 A \(\longrightarrow\) Products, a plot of log t 1/2 vs log a (where a is the initial concentration) will give an intercept equal to which of the following ?

(a)

1/k

(b)

log (1/2 k)

(c)

log (1/k)

(d)

log k

47.

Te half-life of a reaction is halved as the initial concentration of the reactant is doubled. The order of reaction is

(a)

0.5

(b)

(c)

(d)

48.

For a first order reaction, the time required for 99.9% of the reaction to take place is nearly

(a)

10 times that required for half of the reaction

(b)

100 times that required for two - thirds of the reaction

(c)

10 times that required forone - fourth of the reaction

(d)

20 times that required for half of the reaction

49.

t_1/4 can be taken as the time taken for the concentration of a reactant to drop to \(\frac {3}{4}\) of its initial value. If the rate constant for a first order reaction is K, then t_1/4 can be written as

(a)

0.10/K

(b)

0.29/K

(c)

0.69/K

(d)

0.75/K

50.

At 500 K, the half-life period of a gaseous reaction at the initial pressure of 80 kPa is 350 sec. When the pressure is 40 kPa, the half-life period is 175 sec. The order of reaction is

(a)

second

(b)

more than zero but less than first

(c)

zero

(d)

first

51.

For the reaction A + 2 B \(\longrightarrow\) C, the reaction rate is doubled if the increased by four times when concentration of both A and B are increased by four times. The order of reaction is

(a)

(b)

(c)

(d)

52.

Rate constant of a reaction is 0.0693 min^-1. Starting with 10 mol L^-1, rate of reaction after 10 minutes will be

(a)

0.0693 M min ^-1

(b)

0.0693\(\times 2.5\) M min ^-1

(c)

0.0693 \(\times 5\) M min ^-1

(d)

0.0693 \(\times 10\) M min ^-1

53.

The rate constant of a second order reaction, 2A\(\longrightarrow\) Products, is 10^-4 lit mol^-1 min^-1. The initial concentration of the reactant is 10^-2mol lit^-1. What is the half-life (in min) ?

(a)

(b)

1000

(c)

100

(d)

10⁶

54.

For a first order reaction, the time taken to reduce the initial concentration by a factor of \(\frac {1}{4}\) is 20 minutes. The time required to reduce initial concentration by a factor of 1/16 is

(a)

20 min

(b)

10 min

(c)

80 min

(d)

40 min

(e)

5 min

55.

A first order reaction is carried out staring with 10 mol L^-1 of the reactant. It is 40 % complete in one hour. If the same reaction is carried out with an initial concentration of 5 mol L^-1, the percentage of the reaction that is completed in one hour will be

(a)

40 %

(b)

80 %

(c)

20 %

(d)

60 %

56.

For the reaction A + B \(\longrightarrow\) C + D, doubling the concentration of both the reactants increases the reaction rate by 8 times and doubling the concentration of only B simply doubles the reaction rate. The rate law is given as

(a)

r = k[A]^1/2 [B]^1/2

(b)

r = k[A] [B]²

(c)

r = k[A]²[B]

(d)

r = k[A] [B}

57.

For the reaction, Ag+ + 2 NH3 \(\rightleftharpoons \) [Ag(NH3)2]⁺ Then which of the following statement/s is are correct ?

(a)

Rate constant for forward reaction = \(2 \times 10 ^{7}\)

(b)

Rate constant for backward reaction = \(1 \times 10 ^{-2}\)

(c)

Equilibrium constant of the reaction = \(2 \times 10 ^{9}\)

(d)

All the above

58.

The rate law for a reaction between the substances A and B is given by Rate = k[A]ⁿ [B] ^m On doubling the concentration of B, the ratio of the new rate to the earlier rate of the reaction will be

(a)

m+n

(b)

(n-m)

(c)

2^(n-m)

(d)

\(\frac {1}{2^{(m+n)}}\)

59.

In the synthesis of ammonia from nitrogen and hydrogen gases, if 6\(\times 10 ^{-2 }\) mole of hydrogen disappears in 10 minutes, the number of moles of ammonia formed in 0.3 minutes is

(a)

1.8\(\times 10 ^{-2 }\)

(b)

1.2\(\times 10 ^{-2 }\)

(c)

4\(\times 10 ^{-2 }\)

(d)

3.6\(\times 10 ^{-2 }\)

60.

In a catalytic experiment involving Haber's process, N2 (g) + 3 H₂ (g) \(\longrightarrow\) 2 NH₂ (g), the rate of reaction was measured as : Rate = \(\frac { d[{ NH }_{ 3 }] }{ dt } \) = 2.0 \(\times 10 ^{-4} M s^{-1}\) . If there were no side reactions, what was the rate of reaction expressed in terms of N₂ ?

(a)

1\(\times 10 ^{-4} s ^{-1}\)

(b)

4\(\times 10 ^{-4} s ^{-1}\)

(c)

5\(\times 10 ^{-4} s ^{-1}\)

(d)

1\(\times 10 ^{-4} s ^{-1}\)

61.

Which of the following statements are in accordance with the Arhenius equation ?

(a)

Rate of a reaction increases with decrease in temperature

(b)

Rate of a reaction increases with decrease in activation energy

(c)

Rate constant decreases exponentially with increase in temperature

(d)

Rate of reaction decreases with decrease in activation energy

62.

In the graph showing Maxwell Boltzman distribution of energy, ....... .

(a)

area under the curve must not change with increase in temperature

(b)

area under the curve increases with increase in temperature

(c)

area under the curve decreases with increase in temperature

(d)

with increase in temperature curve broadens and shifts to the right hand side.

63.

According to Maxwell Boltzmann distribution of energy, ....... .

(a)

the fraction of molecules with most probable kinetic energy decreases at higher temperatures

(b)

the fraction of molecules with most probable kinetic energy increases at higher temperatures

(c)

most probable kinetic energyincreases at higher temperatures

(d)

most probable kinetic energy decreasesat higher temperatures.

64.

At high pressure, the following reaction is of zero order.
2NH₃ \(\xrightarrow [ Platinum \ catalyst ]{ 1130K } \) (g) N₂(g) + 3H₂(g)
Which of the following options are correct for this reaction ?

(a)

Rate reaction = Rate constant

(b)

Rate of the reaction depends on concentration of amonia

(c)

Rate of decomposition of ammonia will remain constant until ammonia disappears completely

(d)

Further increase in pressure will change the rate of reaction

65.

For a complex reaction ............. .

(a)

order of overall reaction is same as molecularity of the slowest step

(b)

order of overall reaction is less than the molecularity of the lowest step

(c)

order of overall reaction is grater than molecularity of the slowest step

(d)

molecularity of the slowest step is never zero or non integer.

66.

In any unimolecular reaction ........... .

(a)

only one reacting species is involved in the rate determining step

(b)

the order and the molecularity of slowest step are equal to one

(c)

the molecularity of the reaction is one and order is zero

(d)

both molecularity and order of the reaction are one.

67.

Rate law cannot be determined from balanced chemical equation if ........ .

(a)

reverse reaction is involved

(b)

it is an elementary reaction

(c)

it is a sequence of elementary reactions

(d)

any of the reactants is in excess.

68.

The value of rate constant of a pseudo first order reaction ............... .

(a)

depends on the concentration of reactants present in small amount

(b)

depends on the concentration of reactants present in excess

(c)

is independent of the concentration of reactants

(d)

depends only on temperature.

69.

Compounts 'A' and 'B' react according to the following chemical equation :
A (g) + 2 B (g) \(\longrightarrow\) 2 C (g)
Concntration of either 'A' or 'B' were changed keeping the concentration of the reactions constant and rates were measured as a function of initial concentration. Following results were obtained. Choose the correct option for the rate equations for this reaction.

Exp.	Initial concentration of [A]/mol L^-1	Initial concentration of [B]/mol L^-1	Initial rate of formation of [C] mol L^-1 s^-1
1.	0.30	0.30	0.10
2.	0.30	0.60	0.40
3.	0.60	0.30	0.20

(a)

Rate = k[A]²[B]

(b)

Rate = k[A] [B]²

(c)

Rate = k[A] [B]

(d)

Rate = k[A]²[B]⁰

70.

A first order reaction is 50% completed in 1.26\(\times 10^{15} s\) . How much time would it take for 100% completion ?

(a)

1.26 \(\times 10^{15} s\)

(b)

2.52 \(\times 10^{14} s\)

(c)

2.52 \(\times 10^{28} s\)

(d)

infinite

71.

Which of the following statement is incorrect about the collision theory of chemical reaction ?

(a)

If considers reactions molecules or atmos to be hard spheres and ignores their structural features

(b)

Number of effective collisions determines the rate of reaction

(c)

Collision at atoms or molecules possessing sufficient threshold energy results into the product information

(d)

Molecules should collide with sufficient threshold energy and proper orientation for the collision to be effective.

72.

Which of the following statements is not correct about order of a reaction ?

(a)

The order of a reaction can be a fractional number

(b)

Order of a reaction is experimentally determined quantity.

(c)

The order of a reaction is always equal to the sum of the stoichiometric coeffecients of reactants in the balanced chemnical equation for reaction.

(d)

The order of a reaction is the sum of the powers of molar concentration of the reaction in the rate law expression.

73.

Consider the Arrhenius equation given below and mark the correct option. k = Ae^-E_a/RT

(a)

Rate constant increases exponentially with increasing activation energy and decreasing temperature

(b)

Rate constant decreases exponentially with increasing activation energy and decreasing temperature

(c)

Rate constant increases exponentially with decreasing activation energy and decreasing temperature

(d)

Rate constant increases exponentially with decreasing activation energy and increasing temperature

74.

In the presence of a catalyst, the heat evolved or absorbed during the reaction ............ .

(a)

increases

(b)

decreases

(c)

remains unchanged

(d)

may increase or decrease

75.

The role of a catalyst is to change .............. .

(a)

Gibbs energy of reaction

(b)

enthalpy of reaction

(c)

activation energy of reaction

(d)

equilibrium constant

76.

If the activatiopn energy for the forward reaction is 150 kJ mol^-1 and that of the reserve reaction is 260 kJ mol^-1, what is the enthalpy change for the reaction ?

(a)

410 kJ mol^-1

(b)

-110 kJ mol^-1

(c)

110 kJ mol^-1

(d)

-410 kJ mol^-1

77.

The half-life period of a radioactive element is 20 days. What will be the remaining mass of 100 g of it after 60 days?

(a)

25 g

(b)

50 g

(c)

12.5 g

(d)

20 g

78.

10 g of a radioactive isotope is reduced to 1.25 g in 12 years, therefore half-life period of the isotope is

(a)

24 years

(b)

4 years

(c)

3 years

(d)

8 years

79.

If a graph is plotted between In k ad 1/T for the first order reaction. the slope of the straight line so obtained is given by

(a)

-\(\frac {E_a}{R}\)

(b)

-\(-\frac {E_a}{2.303 R}\)

(c)

\(-\frac {2.303} {E_aR}\)

(d)

\(-\frac {E_a}{2.303 }\)

80.

75% of the first order reaction was completed in 32 min. 50% of the reaction was completed in

(a)

24 min

(b)

8 min

(c)

16 min

(d)

4 min

81.

The reaction A \(\longrightarrow\) B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hour. What is the time taken for conversion of 9.9 mole of A to produce 0.675 mole of B ?

(a)

1 hour

(b)

0.5 hour

(c)

0.25 hour

(d)

2 hours

82.

For the reaction R \(\longrightarrow\) P, a graph of [R] against time is found to be a straight line with negative slope. What is the order of reaction ?

(a)

Second order

(b)

Third order

(c)

First order

(d)

Zero order

83.

The molecularity and order of the reaction 2 NO (g) + O₂ (g) \(\rightarrow\)2NO₂ (g) are respectively

(a)

one and one

(b)

two and two

(c)

three and three

(d)

two and three

84.

Rate constant of a reaction (k) is 175 litre² mol^-2 sec^-1. What is the order of reaction?

(a)

first

(b)

second

(c)

third

(d)

zero

85.

A first order reaction has a half-life period of 34.65 seconds. Its rate constant is

(a)

2 \(\times 10\) ^-2 sec^-1

(b)

4 \(\times 10\) ^-4 sec^-1

(c)

20 sec^-1

(d)

2 \(\times 10\) ^-4 sec^-1

86.

The rate of the reaction 2 NO + CI₂ \(\rightarrow\) 2NOCI is given by the rate equation : rate = k [NO]₂ [CI₂]. The value of the rate constant can be increased by

(a)

increasing the temperature

(b)

increasing the concentration of NO

(c)

increasing the concentration of CI₂

(d)

doing all of these

87.

In a reaction \(\longrightarrow\) B, the rate of reaction increases two times on increasing the concentration of the reactant four times, then order of reaction is

(a)

(b)

(c)

1/2

(d)

88.

The rate of a gaseous reaction is given by the expression k [A][B]. If the volume of the reaction vessel is suddenly reduced to 1/4 th of the initial volume, the reaction rate relating to original rate will be

(a)

1/10

(b)

1/8

(c)

(d)

89.

Time required for 100 percent completion of a zero order reaction is

(a)

\(\frac {2k}{a}\)

(b)

\(\frac {a}{2k}\)

(c)

\(\frac {a}{k}\)

(d)

a k

90.

In the reaction BrO^-₃ (aq) + 5 Br ^- (aq) + 6 H⁺ \(\longrightarrow\) 3 Br₂(I) + 3 H₂O (l), the rate of apperance of bromine (BHr₂) is related to the disapearance of bromide uions as follows :

(a)

\(\frac { d[{ Br }_{ 2 }] }{ dt } =-\frac { 5 }{ 3 } \frac { d[{ Br }^{ - }] }{ dt } \)

(b)

\(\frac { d[{ Br }_{ 2 }] }{ dt } =\frac { 5 }{ 3 } \frac { d[{ Br }^{ - }] }{ dt } \)

(c)

\(\frac { d[{ Br }_{ 2 }] }{ dt } =\frac {3 }{ 5} \frac { d[{ Br }^{ - }] }{ dt } \)

(d)

\(\frac { d[{ Br }_{ 2 }] }{ dt } =-\frac { 3 }{ 5 } \frac { d[{ Br }^{ - }] }{ dt } \)

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Answers Key:

Multiple Choice Question

90 x 1 = 90

(b)
2.0

(a)
\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}]\)

(b)
166

(a)
60 min

(a)
30

(a)
zero

10.

(a)
138.6 s

11.

(d)
E_a

12.

(b)
0.5 x 10^{- 3} s^-1

13.

(b)
\( \ln A ;-\frac{E_{\alpha}}{R}\)

14.

15.

(d)
\(\log k-\left(\frac{E_{a}}{R T}\right)=A\)

16.

(d)
pseudo first order reaction

17.

(b)
\(t_{1 / 2}=\frac{[R]_{0}}{2 k}\)

18.

(a)
\(\frac{2.303}{10}\) log 5 min^-1

19.

(a)
\( k=\frac{2.303}{t} \log _{10} \frac{a}{(a-x)}\)

20.

21.

(b)
half

22.

(d)
zero

23.

(a)
Zero order reaction

24.

(d)
one

25.

(b)
increases

26.

(a)
0.187 M min^-1

27.

(b)
Hydrolysis of starch

28.

(d)
the reaction proceeds to 99/6% completion in eight half-duration

29.

30.

(a)
1 \(\times 10 ^{-4}\)

31.

32.

(b)
(ii) and (v)

33.

(b)
2.4 atm

34.

(b)
collosion theory is not applicable to unimolecular reaction

35.

(d)
\(\frac {1000}{2.303}K\)

36.

37.

(a)
less than \(\triangle H\)

38.

(a)
5 kJ mol^-1

39.

40.

(a)
60.5 kJ mol^-1

41.

(a)
In k vs \(\frac {1}{T}\)

42.

43.

(b)
\({ r }_{t }\frac {1}{2}({ r }_{0 }+{ r }_{ \infty })\)

44.

(b)
3

45.

(a)
0.5 mol^-1dm³

46.

(d)
log k

47.

48.

(a)
10 times that required for half of the reaction

49.

(b)
0.29/K

50.

(d)
first

51.

52.

53.

(d)
10⁶

54.

(d)
40 min

55.

(a)
40 %

56.

57.

(d)
All the above

58.

59.

(b)
1.2\(\times 10 ^{-2 }\)

60.

(a)
1\(\times 10 ^{-4} s ^{-1}\)

61.

(b)
Rate of a reaction increases with decrease in activation energy

62.

Area under the curve must remain the same because sum of all fractions must be equal to i.e., total probability is one. Hence, (a) is incorrect. Also (d) is correct and (b),(c) are wrong.

63.

(a)
the fraction of molecules with most probable kinetic energy decreases at higher temperatures

64.

65.

(d)
molecularity of the slowest step is never zero or non integer.

66.

(a)
only one reacting species is involved in the rate determining step

67.

(a)
reverse reaction is involved

68.

The value of rate constant of a pseudo first order reaction depends not only on temperaturebut also on concentration of reactant present in excess (See Solved Problem 2, page 4/42). Hence, (b) is correct

69.

(b)
Rate = k[A] [B]²

70.

Whole of the substance never reacts because in every half life, 50% of the substance reacts. Hence, time taken for 100% completion of a reaction is infinite.

71.

(c) is incorrect because formation of product depends not only on energy but also on proper orientation at the time of colllision.

72.

(c)
The order of a reaction is always equal to the sum of the stoichiometric coeffecients of reactants in the balanced chemnical equation for reaction.

73.

(d)
Rate constant increases exponentially with decreasing activation energy and increasing temperature

74.

75.

In the presence of catalyst , activation energy barrier is lowerd.

76.

(b)
-110 kJ mol^-1

77.

(c) : 60 days = 3 half-lives, i.e., n = 3 ; [A] = \(\frac { [A]_{ 0 } }{ { 2 }^{ n } } =\frac { 100 }{ { 2 }^{ 3 } } =\frac { 100 }{ 8 } =12.5g\)

78.

(b)
4 years

79.

(b)
-\(-\frac {E_a}{2.303 R}\)

80.

81.

(a) : The fraction of a reacted in each case is same (0.2/0.8 = 1/4), (0.9 - 0.675)/0.90 = 0.225/0.90 = 1/4). Hence, time taken is same.

82.

(d) : For zero order reaction, k = \(\frac {1}{t}\)\(\left[ { \left[ A \right] }_{ 0 }-\left[ A \right] \right] \) or \( { \left[ A \right] }-\left[ A \right] _{ 0 } - kt\)

83.

84.

85.

(a) : \(k = \frac {0.693}{t/2}= \frac {0.693}{34.65}s^{-1} = 2 \times 10^{-2}\)s^-1

86.

(a) : The rate of constant of a reaction depends only on temperature and does not depend upon concentrations of the reactants.

87.

(c) : (i) r = k \(a ^ { \alpha}\) (ii) 2 r = k (4 a) ^{^\(\alpha\)}dividing (ii) by (i), 4^{^\(\alpha\)}= 2 or 2 \(\alpha\)= 1/2

88.

(d) : Rate = k ab. When volume is reduced to 1/4 th, Concentrations will become = 4 times

New rate = k (4 a) (4 b) = 16 k ab = 16 times.

89.

90.

(d) \(\frac{1}{3} \frac { d[{ Br }_{ 2 }] }{ dt } =-\frac { 1 }{ 5 } \frac { d[{ Br }^{ - }] }{ dt } \) or \(\frac { d[{ Br }_{ 2 }] }{ dt } =-\frac {3 }{ 5 } \frac { d[{ Br }^{ - }] }{ dt } \)