# SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 chapter 6 - Chemical Kinetics [Latest edition]

## Chapter 6: Chemical Kinetics

Multiple choice questions

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 6 Chemical Kinetics Multiple choice questions

#### 1 mark

Multiple choice questions | Q 1

A First order reaction is 50% complete in 69.3 minutes. Time required for 90% completion for the same reaction is _______.

• 230.3 min

• 100 min

• 230 min

• 125 min

Multiple choice questions | Q 2

Time required for 100% completion of a zero order reaction is _______.

• a/k

• a/2k

• a.k

• 2k/a

Multiple choice questions | Q 3

Rate constant of a reaction is 3.6 × 10–3 s–1. The order of reaction is ______.

• first

• second

• third

• zero

Multiple choice questions | Q 4

The rate law relates to the rate of a chemical reaction in terms of _______.

• concentration of catalyst

• temperature

• potential energy

• mol/L of reactants

Multiple choice questions | Q 5

For first order reaction, the rate constant for the decomposition of N2O5 is 6 × 10–4 s –1. The half-life period for decomposition in seconds is ______.

• 11.55

• 115.5

• 1155

• 1.155

Multiple choice questions | Q 6

Order of reaction for which unit of rate constant is mol dm–3 s–1 is _______.

• 1

• 3

• 0

• 2

Multiple choice questions | Q 7

The rate of catalysed reaction is large than the uncatalysed reaction as _______.

• Ea is larger

• Ea is lower

• Ea is same

• threshold energy is absent

Multiple choice questions | Q 8

Which of the following is a unimolecular reaction?

• 2HI → H2 + I2

• N2O5 → N2O4 + ½O2

• H2 + Cl2 → 2HCl

• PCl3 + Cl2 → PCl5

Multiple choice questions | Q 9

Effect of catalyst in a chemical reaction is to change the _______.

• activation energy

• equilibrium concentration

• final products

• heat of a reaction

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 6 Chemical Kinetics Very short answer questions

#### 1 Mark

Very short answer questions | Q 1

Give one example of pseudo first-order reaction.

Very short answer questions | Q 2

Write order of the following reaction:

$\ce{2NH_{3(g)} -> N_{2(g)} + 3H_{2(g)}}$

Very short answer questions | Q 3

Identify molecularity of following reaction:

$\ce{C2H5I_{(g)} -> C2H_{4(g)} + HI_{(g)}}$

Very short answer questions | Q 4

Rate constant for the reaction 2N2O5 → 4NO2 + O2 is 4.98 × 10–4 s–1. Find the order of reaction?

Very short answer questions | Q 5

Write a mathematical expression for integrated rate law for zero-order reaction.

Very short answer questions | Q 6

Name the slowest step that determines the rate in a complex reaction.

Very short answer questions | Q 7

Give one example of zero order reaction.

Very short answer questions | Q 8

For the reaction $\ce{2NO_{(g)} + 2H_{2(g)} -> N_{2(g)} + 2H2O_{(g)}}$,

The rate law is, rate = k[NO]2 [H2].

What is the overall order of reaction?

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 6 Chemical Kinetics Short answer questions (Type- I)

#### 2 Marks

Short answer questions (Type- I) | Q 1

What is half life of first order reaction if time required to decrease concentration of reactants from 0.8 M to 0.2 M is 12 hours?

Short answer questions (Type- I) | Q 2

Distinguish between : Order and Molecularity of reaction

Short answer questions (Type- I) | Q 3

For the reaction 2NOBr → 2NO2 + Br2, the rate law is rate = k[NOBr]2. If the rate of a reaction is 6.5 × 10–6 mol L–1 s–1, when the concentration of NOBr is 2 × 10–3 mol L–1. What would be the rate constant of the reaction?

Short answer questions (Type- I) | Q 4

Write four key points about order of reaction.

Short answer questions (Type- I) | Q 5

Explain pseudo first order reaction with a suitable example.

Short answer questions (Type- I) | Q 6

Define order of reaction with suitable examples.

Short answer questions (Type- I) | Q 7

Explain with the help of a potential energy diagram that the catalyst increases the rate of the reaction.

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 6 Chemical Kinetics Short answer questions (Type- II)

#### 3 Marks

Short answer questions (Type- II) | Q 1

Derive an integrated rate law expression for first order reaction: A → B + C

Short answer questions (Type- II) | Q 2

Define molecularity.

Short answer questions (Type- II) | Q 2

The rate constant of the first order reaction is 1.386 min–1. Calculate the time required for 80% reactant to decompose?

Short answer questions (Type- II) | Q 3

A reaction occurs in the following steps:

Step 1: $\ce{NO_{2(g)} + F_2 -> NO2F_{(g)} + F_{(g)}}$ (slow)

Step 2: $\ce{F_{(g)} + NO_{2(g)} -> NO_2F}$ (Fast)

1. Write the equation of overall reaction.
2. Write the rate law.
3. Identify reaction intermediate.
Short answer questions (Type- II) | Q 4

Define half life of a reaction.

Short answer questions (Type- II) | Q 4

Write units of rate constants for:

1. First-order reaction
2. Zero-order reaction
Short answer questions (Type- II) | Q 5

Write an expression for instantaneous rate of reaction:

2N2O(g) → 4NO2(g) + O2(g).

What is the order of reaction?

Short answer questions (Type- II) | Q 6

Why is molecularity applicable for only elementary reactions whereas order of a reaction is applicable for elementary and complex reactions? Explain with suitable examples.

Short answer questions (Type- II) | Q 7

For a zero-order reaction, molecularity can never be equal to zero. Explain.

Short answer questions (Type- II) | Q 8

For the reaction 2A + B → C, rate of disappearance of A 0.076 mol s –1.

1. What is the rate of formation of C?
2. What is the rate of consumption of B?
3. What is the rate of the overall reaction?

### SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 Chapter 6 Chemical Kinetics Long answer questions

#### 4 Marks

Long answer questions | Q 1

In a first-order reaction A → B, 60% of a given sample of a compound decomposes in 45 mins. What is the half-life of reaction? Also, write the rate law equation for the above first-order reaction.

Long answer questions | Q 2

Derive an expression for the relation between half-life and rate constant for first-order reaction.
The half-life period for the first order reaction is 1.7 hrs. How long will it take for 20% of the reactant to disappear?

Long answer questions | Q 3

Give one example of the reaction where order and molecularity are the same.
Mention any two factors that influence the rate of chemical reaction.
If for the reaction A → products, a straight line graph passing through origin is obtained between the rate of reaction against concentration of A, what would be the order of reaction? Why?

## SCERT Maharashtra Question Bank solutions for 12th Standard HSC Chemistry Maharashtra State Board 2021 chapter 6 - Chemical Kinetics

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Concepts covered in 12th Standard HSC Chemistry Maharashtra State Board 2021 chapter 6 Chemical Kinetics are Chemical Kinetics, Rate of Reactions, Rate of Reaction and Reactant Concentration, Molecularity of Elementary Reactions, Integrated Rate Law, Collision Theory of Bimolecular Reactions, Temperature Dependence of Reaction Rates, Effect of a Catalyst on the Rate of Reaction.

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