Q: The pre-exponential factor in the Arrhenius equation of a second order reaction has the units

k=Ae−Ea/RT Since e−Ea/RT is dimensionless So unit of A= Unit of k. ∴ For second order reaction unit of A is L⋅mol−1 s−1.

Q: A radioactive isotope having a half-life of three days was received after 12 days. It was found that there were 3 g of isotope in the container. The initial weight of the isotope when packed was

(d) n=312=4 Nt=N0[21]n 3=N0[21]4 ∴N0=48 gram

Q: Consider the chemical reaction, N2( g)+3H2( g)⟶2NH3( g) The rate of this reaction can be expressed in terms of time derivatives of concentration of N2( g),H2( g) or NH3( g). Identify the correct relationship amongst the rate expression:

(a) N2( g)+3H2(g)→2NH3( g) dt−d[ N2]=−31dtd[H2]=21dtd[NH3]

Q: For a reaction: X( g)→Y( g)+Z( g) The half-life period is 10 min. In what period of time would be concentration of X be reduced to 10% of original concentration?

(b) t1/2=10 min a=a0=100 and a−x=10K=t2.303log10100=100.6932

Q: In a first order reaction the concentration of reactant decreases from 800 mol/dm3 to 50 mol/dm3 in 2×102 sec. The rate constant of reaction in sec−1 is

(c) K=2×1022.303log50800=1.386×10−2 s−1

Question 1

The rate law for the dimerisation of NO2​ is dt−d[NO2​]​ =k[NO2​]2 Which of the following changes will change the value of the specific rate constant, k ?

Accepted Answer

(b) K depends only on temperature

Question 2

The temperature coefficient of a reaction is

Accepted Answer

(b)
kT​kT+10​​≈2 to 3

Question 3

The rate of a chemical reaction generally increases rapidly even for small temperature increase because of rapid increase in the

Accepted Answer

(b) Fraction of molecules with energy more than energy barrier increases

Question 4

The pre-exponential factor in the Arrhenius equation of a second order reaction has the units

Accepted Answer

k=Ae−Ea​/RT
Since e−Ea​/RT is dimensionless
So unit of A= Unit of k.
∴ For second order reaction unit of A is L⋅mol−1 s−1.

Question 5

A catalyst is a substance which

Accepted Answer

(c) A catalyst decreases the activation energy.

Question 6

Which reaction characteristics is/are changing by the addition of a catalyst to a reaction at constant temperature

Accepted Answer

(a) A catalyst decreases the activation energy.

Question 7

A radioactive isotope having a half-life of three days was received after 12 days. It was found that there were 3 g of isotope in the container. The initial weight of the isotope when packed was

Accepted Answer

(d) n=312​=4
Nt​=N0​[21​]n
3=N0​[21​]4
∴N0​=48 gram

Question 8

If uranium (mass number 238 and atomic number 92) emits an α-particle, the product has mass number and atomic number:

Accepted Answer

(b) 92​U238⟶90​Th234+2​He4

Question 9

Consider the chemical reaction, N2​( g)+3H2​( g)⟶2NH3​( g) The rate of this reaction can be expressed in terms of time derivatives of concentration of N2​( g),H2​( g) or NH3​( g). Identify the correct relationship amongst the rate expression:

Accepted Answer

(a) N2​( g)+3H2​(g)→2NH3​( g)
dt−d[ N2​]​=−31​dtd[H2​]​=21​dtd[NH3​]​

Question 10

Rate law for the following reaction: Ester +H+⇌ Acid + Alcohol; is dtdx​=k[ ester ]1[H+]0. What would be the effect on the rate if concentration of H+ion is doubled?

Accepted Answer

(a) Rate equation shows that it does not depend on the concentration of (H+)

Question 11

Consider a reaction aG+bH⟶ Product. When concentration of both the reactants G and H is doubled, the rate increases by eight times. However, when concentration of G is doubled keeping the concentration of H constant, the rate is doubled. The overall order of the reaction is

Accepted Answer

(d) x=1y=2 overall is 3

Question 12

What is the order of a reaction which has a rate expression rate =k[A]3/2[B]−1

Accepted Answer

(b) Order =3/2−1=21​

Question 13

The kinetic data for the reaction: 2A+B2​⟶2AB are as given below.
[A]molL−10.51.00.5​[ B2​]molL−11.01.02.0​ Rate molL−1 min−12.5×10−35.0×10−31×10−2​
Hence the order of reaction with respect to A and B2​ are, respectively,

Accepted Answer

(a) Rate =K[A]m[B2​]n

Question 14

Units of rate constant of first and zero order reactions in terms of molarity unit are respectively

Accepted Answer

(a) Rate = Time  Concentration ​

Question 15

For a reaction: X( g)→Y( g)+Z( g) The half-life period is 10 min. In what period of time would be concentration of X be reduced to 10% of original concentration?

Accepted Answer

(b) t1/2​=10 min           a=a0​=100    and a−x=10​K=t2.303​log10100​=100.6932​

Question 16

In a first order reaction the concentration of reactant decreases from 800 mol/dm3 to 50 mol/dm3 in 2×102 sec. The rate constant of reaction in sec−1 is

Accepted Answer

(c) K=2×1022.303​log50800​=1.386×10−2 s−1

Question 17

Half-life period of a first order reaction is

Accepted Answer

(b) t1/2​∝an−11​∴n=1

Question 18

In the first order reaction, the concentration of the reactant is reduced to 25% in one hour. The half life period of the reaction is

Accepted Answer

(c) t1/2​=0.5hr

Question 19

Under the same reaction conditions, initial concentration of 1.386 moldm−3 of a substance becomes half in 40 seconds and 20 seconds through first order and zero order kinetics, respectively. Ratio (k0​)(k1​)​ of the rate constants for first order (k1​) and zero order (k0​) of the reaction is

Accepted Answer

(a)
t1/21​=K1​0.693​t1/20​=2K0​a​​

Question 20

A radioactive element resembling iodine in properties is

Accepted Answer

(a) Astatine as it belongs to halogen

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Solutions for Physical Chemistry II for IIT JEE Main and Advance by Ranveer Singh

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