chemistry MCQs - 10th class Chapter 01 Mcqs

1

Reactions that proceed in both forward and reverse directions are called?

A

Irreversible reactions

B

Reversible reactions

C

Complete reactions

D

Static reactions

2

In an irreversible reaction, reactants are represented on the left and products on the right, separated by a?

A

Double arrow (⇌)

B

Single arrow (→)

C

Plus sign (+)

D

Equal sign (=)

3

Dynamic equilibrium means that the reaction is?

A

Stopped

B

Still continuing

C

Completed

D

Only proceeding forward

4

At equilibrium, the rate of the forward reaction is ________ the rate of the reverse reaction.

A

Greater than

B

Less than

C

Equal to

D

Half of

5

Who put forward the Law of Mass Action in 1869?

A

Dalton and Newton

B

Guldberg and Waage

C

Avogadro and Boyle

D

Lavoisier and Priestley

6

In the expression for the equilibrium constant, the concentrations of the products are written in the?

A

Denominator

B

Exponent

C

Numerator

D

Base

7

A reaction with a large Kc value will have?

A

More reactants than products

B

More products than reactants

C

Equal amounts of reactants and products

D

No products at all

8

The active mass of a substance is generally considered its molar concentration, expressed in units of?

A

g dm⁻³

B

mol dm⁻³

C

kg cm⁻³

D

mol cm⁻³

9

For the reaction H₂(g) + I₂(g) ⇌ 2HI(g), the units for Kc are?

A

mol dm⁻³

B

mol⁻¹ dm³

C

mol² dm⁻⁶

D

No units

10

What does a very small numerical value of Kc (e.g., 3.0 x 10⁻⁹) indicate?

A

The reaction goes to completion

B

The reaction has almost all products at equilibrium

C

The reaction has almost all reactants at equilibrium

D

The reaction is very fast

11

Dynamic equilibrium is achievable only in a an?

A

Open system

B

Isolated system

C

Closed system

D

Unregulated system

12

In the reaction of hydrogen and iodine, what is the color of iodine vapor?

A

Colourless

B

Green

C

Purple

D

Red-brown

13

When CaCO₃ is heated in an open flask, the reaction goes to completion because?

A

CaO is unstable

B

CO₂ gas escapes

C

The reaction is slow

D

It is an endothermic reaction

14

The state where the reaction ceases to proceed is called?

A

Dynamic equilibrium

B

Chemical equilibrium

C

Static equilibrium

D

Reversible equilibrium

15

According to the Law of Mass Action, the rate of a reaction is directly proportional to the product of the ________ of reacting substances.

A

Volumes

B

Temperatures

C

Pressures

D

Active masses

16

The value of Kc depends only on?

A

Pressure

B

Initial concentration

C

Temperature

D

Catalyst

17

If the reaction quotient Qc is less than Kc, the reaction will proceed in the?

A

Forward direction

B

Reverse direction

C

It is at equilibrium

D

It will stop

18

If the reaction quotient Qc is greater than Kc, the reaction will proceed in the?

A

Forward direction

B

Reverse direction

C

It is at equilibrium

D

It will speed up

19

What is the term for the numerical value obtained when concentrations at any time 't' are put into the equilibrium constant expression?

A

Equilibrium Constant (Kc)

B

Rate constant (k)

C

Reaction Quotient (Qc)

D

Avogadro's number

20

For the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), the correct Kc expression is?

A

[NH₃]² / ([N₂][H₂])

B

[N₂][H₂]³ / [NH₃]²

C

[NH₃]² / ([N₂][H₂]³)

D

([N₂][H₂]³) * [NH₃]²

21

A reaction with a moderate Kc value has?

A

Only products

B

Only reactants

C

Comparable amounts of reactants and products

D

No reaction

22

What happens to the rate of the forward reaction as a reversible reaction proceeds towards equilibrium?

A

It increases

B

It stays constant

C

It decreases

D

It becomes zero

23

What happens to the rate of the reverse reaction as a reversible reaction proceeds towards equilibrium?

A

It increases

B

It stays constant

C

It decreases

D

It becomes zero

24

The decomposition of hydrogen iodide (2HI → H₂ + I₂) is an example of a?

A

Forward reaction

B

Reverse reaction

C

Irreversible reaction

D

Static reaction

25

Active mass is represented by using?

A

Parentheses ( )

B

Curly brackets { }

C

Square brackets [ ]

D

Angle brackets < >

26

In the context of the H₂(g) + I₂(g) ⇌ 2HI(g) reaction, hydrogen iodide (HI) is?

A

Purple

B

Blue

C

Yellow

D

Colourless

27

The specific rate constant for the forward reaction is denoted by?

A

kr

B

kf

C

Kc

D

Qc

28

The specific rate constant for the reverse reaction is denoted by?

A

kr

B

kf

C

Kc

D

Qc

29

Equilibrium is a state of?

A

Inactivity

B

Balance

C

Completion

D

Initiation

30

The lives of aquatic plants and animals are related to the concentration of dissolved ________ in water.

A

Nitrogen

B

Carbon dioxide

C

Oxygen

D

Hydrogen

31

Which of the following is a characteristic of a reverse reaction?

A

It takes place from left to right

B

Its rate is very fast at the initial stage

C

It slows down gradually

D

It speeds up gradually

32

At equilibrium, the macroscopic properties like color and density?

A

Change continuously

B

Become zero

C

Remain the same

D

Increase

33

An equilibrium state can be attained starting from?

A

Reactants only

B

Products only

C

Either reactants or products

D

Only in the presence of a catalyst

34

The reaction 2CO(g) + O₂(g) ⇌ 2CO₂(g) has a very large Kc (2.2 x 10²²). This means the reaction?

A

Never completes

B

Is very slow

C

Goes almost to completion

D

Has mostly reactants at equilibrium

35

The decomposition of ammonia 2NH₃(g) ⇌ N₂(g) + 3H₂(g) has a very small Kc (3.0 x 10⁻⁹). This means?

A

The reaction favors product formation

B

The reaction mixture contains mostly NH₃

C

The reaction is irreversible

D

The reaction is very fast

36

The synthesis of ammonia from nitrogen and hydrogen is known as the?

A

Contact process

B

Haber's process

C

Ostwald's process

D

Solvay process

37

For the reaction 2NO₂(g) ⇌ N₂O₄(g), if [NO₂] is the concentration of the reactant, how is it represented in the rate expression?

A

[NO₂]

B

[NO₂]²

C

2[NO₂]

D

[N₂O₄]/[NO₂]

38

If a reaction has an equal number of moles of reactants and products, Kc will have?

A

Units of mol dm⁻³

B

Units of mol⁻¹ dm³

C

No units

D

Units of mol² dm⁻⁶

39

The reaction quotient Qc is used to?

A

Calculate the reaction speed

B

Predict the direction of a reaction

C

Determine the temperature

D

Measure the amount of reactants used

40

When a reversible reaction reaches equilibrium, the concentrations of reactants and products?

A

Become zero

B

Become equal

C

Become constant

D

Keep changing

41

The forward reaction in H₂(g) + I₂(g) ⇌ 2HI(g) is the?

A

Decomposition of HI

B

Combination of H₂ and I₂

C

Reaction of H₂ with HI

D

Reaction of I₂ with HI

42

In the example CaCO₃(s) ⇌ CaO(s) + CO₂(g), the system reaches equilibrium in a?

A

Beaker

B

Test tube

C

Open flask

D

Closed flask

43

A reaction that is supposed to go to completion is a(n) ________ reaction.

A

Reversible

B

Slow

C

Irreversible

D

Equilibrium

44

The concept of active mass is central to the?

A

Law of Conservation of Mass

B

Law of Definite Proportions

C

Law of Mass Action

D

First Law of Thermodynamics

45

The ratio kf / kr is equal to?

A

Qc

B

k (rate constant)

C

Kc

D

[Products]/[Reactants] at time t

46

Which atmospheric gas is used to prepare ammonia for fertilizers?

A

Oxygen

B

Argon

C

Carbon dioxide

D

Nitrogen

47

Oxygen from the atmosphere is used to prepare sulphur dioxide, which is then used to make?

A

Nitric acid

B

Hydrochloric acid

C

Sulphuric acid

D

Acetic acid

48

At the start of a reversible reaction, the rate of the reverse reaction is?

A

Maximum

B

Equal to the forward rate

C

Negligible

D

Constant

49

The reaction N₂O₄(g) ⇌ 2NO₂(g) with Kc = 0.211 is an example of a reaction with?

A

A large Kc value

B

A small Kc value

C

A moderate Kc value

D

No Kc value