Chemical Kinetics Test

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Chemical Kinetics Test - 5

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Weekly Quiz Competition

Question 1
1 / -0.25

Which among the following statement is not true for catalyst?

A
They are not consumed by the reaction

B
They increases or decreases the rate of reaction

C
They changes the equilibrium constant

D
Small quantity is used to carry out reaction

Solution

Catalyst doesnot change the equilibrium constant it only helps in reaching the equilibrium at a faster rate.
Question 2
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A first order reaction is 50% completed in 1.26 ×10¹⁴ s. How much time would it take for 100% completion?

A
1.26 ×10¹⁵ s

B
2.52 ×10¹⁴ s

C
2.52 ×10²⁸ s

D
infinite

Solution

The time taken for half the reaction to complete, i.e., the time in which the concentration of a reactant is reduced to half of its original value is called half-life period of the reaction. But it is impossible to perform 100% of the reaction. 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.
Question 3
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Collision theory is applicable to

A
First order reaction

B
Bimolecular reaction

C
Zero order reaction

D
Pseudo order reaction

Solution

Collision theory is only applicable to bimolecular reaction.
Question 4
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Rate of reaction does not remain constant throughout because

A
Temperature of reactants keep on changing

B
Density of reactants keep on changing

C
Volume of reactants keep on changing

D
Concentration of reactants keep on changing

Solution

Rate of reaction is dependent on concentration of reactant
Question 5
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The unit of rate constant for a first order reaction is

A
Mol/L

B
Mol² / L² / S²

C
S^-1

D
Mol/L/S

Solution

The correct answer is Option C.

Let R be the rate of reaction.
For first order reaction,
R=K[A]¹
⇒K=R[A]^-1
Whereas, K and [A] are rate constant and initial concentration of reactant respectively.
Therefore,
Unit of rate constant =(mol L^-1 )^1-n sec^-1
For first order reaction, n=1
Unit of rate constant = sec^-1
Hence the unit of rate constant for first order reaction is sec^-1 .
Question 6
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Reaction which takes place in one step is known as

A
Unimolecular reaction

B
Bimolecular reaction

C
Elementary reaction

D
Reaction rate

Solution

Elementary reaction are one step reactions.
Question 7
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Which among the following statement is not true for rate constant of a reaction?

A
Rate constant depend upon the concentration of the reactants

B
Unit of rate constant depend upon the order of reaction

C
Rate constant has a definite value at a particular temperature

D
Rate constant changes with temperature

Solution

Rate constant is independent of concentration of reactant.
Question 8
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Which among the following is an example of pseudo first order reaction?

A
Decomposition of hydrogen peroxide

B
Dehydration of oxalic acid

C
Acid catalysed hydrolysis of ethyl acetate

D
Decomposition of nitrogen pentoxide

Solution

In acid catalysed hydrolysis of ethylacetate the water is in excess so it is pseudo 1st order reaction.
Question 9
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Which among the following is an example of first order reaction?

A
Acid catalysed hydrolysis of ethyl acetate

B
Formation and dissociation of ozone

C
Inversion of cane sugar

D
Decomposition of nitrogen pentoxide

Solution

Decomposition of N₂ O₅ is 1st order reaction.
Question 10
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The rate law for the reaction is given by rate = k[RCl]. The rate for this reaction

A
is doubled by doubling the concentration of NaOH

B
is halved by doubling the concentration of NaOH

C
is unaffected by change in temperature

D
is halved by half by reducing the concentration of RCl

Solution

Since order of reaction with respect to RCl is one so if conc of RCl is halfed the rate of reaction will also become half.
Question 11
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For an endothermic reaction, the minimum value for the energy of activation in terms of will be

A
Equal to ΔH

B
More than ΔH

C
Less than ΔH

D
Zero

Solution
Question 12
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Order of the photochemical reaction occurring between hydrogen and chlorine is

A
Third order

B
Second order

C
First order

D
Zero order

Solution

Photochemical reaction between H₂ and Cl₂ is 0 zero wrt to reactants.
Question 13
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The temperature coefficient of most of the reactions lies between

A
1 and 4

B
2 and 3

C
1 and 3

D
2 and 4

Solution

For every 100 rise in temperature rate of reaction increases by factor of 2 or 3.
Question 14
1 / -0.25

Following mechanism has been proposed for a reaction

The rate law expression for the reaction is

A
r = k[A][B]

B
r = k[A]² [B]

C
r = k[A][C]

D
r = k[A]²

Solution

Rate of reaction is determined by slowest step.
Question 15
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The expression which gives 3/4th life of first order reaction is

A

B

C

D

Solution