chemistry MCQs - 9th class Chapter 06 Mcqs

1

A reaction that moves in the forward direction only and goes to completion is called?

A

a reversible reaction

B

an irreversible reaction

C

a dynamic equilibrium

D

a physical change

2

What symbol is used to denote a reversible reaction?

A

→

B

↔

C

0

D

Δ

3

In the Haber process for ammonia synthesis, what are the reactants?

A

N₂ and O₂

B

H₂ and O₂

C

N₂ and H₂

D

CO and H₂

4

A reversible reaction is said to be in a state of chemical equilibrium when?

A

the rate of forward reaction is greater than the reverse reaction

B

the rate of reverse reaction is greater than the forward reaction

C

the rate of forward reaction is equal to the rate of reverse reaction

D

the reaction stops completely

5

What is the color of hydrated copper sulphate pentahydrate (CuSO₄·5H₂O)?

A

White

B

Pink

C

Blue

D

Purple

6

When hydrated copper sulphate is heated strongly, it loses water and turns into?

A

Anhydrous copper sulphate

B

Hydrated cobalt chloride

C

Anhydrous cobalt chloride

D

Calcium oxide

7

What is the color of anhydrous cobalt chloride (CoCl₂)?

A

Pink

B

Purple

C

White

D

Blue

8

What happens to the concentrations of reactants and products at dynamic equilibrium?

A

They continuously change

B

They become zero

C

They remain constant

D

They increase

9

For a dynamic equilibrium to be set up, the system must be?

A

an open system

B

a closed system

C

at high temperature

D

at low pressure

10

What is produced when coal is made to react with steam?

A

CH₄ and H₂O

B

CO₂ and H₂

C

CO and H₂

D

N₂ and O₂

11

The formation of ammonia from nitrogen and hydrogen is an example of what type of reaction in the forward direction?

A

Endothermic

B

Exothermic

C

Physical

D

Decomposition

12

How does an increase in temperature affect the equilibrium of an exothermic reaction like ammonia synthesis?

A

Pushes the reaction in the forward direction

B

Pushes the reaction in the backward direction

C

It has no effect

D

It stops the reaction

13

A change in pressure will disturb the equilibrium state of which type of gaseous reactions?

A

Reactions with equal moles of gaseous reactants and products

B

Reactions with no gaseous species

C

Reactions with different moles of gaseous reactants and products

D

All reactions

14

In the reaction N₂(g) + 3H₂(g) ↔ 2NH₃(g), how does increasing the pressure affect the equilibrium?

A

Shifts to the left (reactants)

B

Shifts to the right (products)

C

No effect

D

Increases volume

15

What is the effect of a catalyst on a reversible reaction at equilibrium?

A

It increases only the forward reaction rate

B

It increases only the backward reaction rate

C

It increases both the forward and backward reaction rates equally

D

It changes the equilibrium position

16

The primary role of a catalyst in a reversible reaction is to?

A

increase the yield of products

B

decrease the time to reach equilibrium

C

shift the equilibrium to the right

D

make the reaction irreversible

17

In the decomposition of calcium carbonate (CaCO₃ ↔ CaO + CO₂), carrying out the reaction in an open container forces it to completion because?

A

CaO is removed

B

CO₂ escapes into the atmosphere

C

the temperature is high

D

the pressure is low

18

What is the color of hydrated cobalt chloride hexahydrate (CoCl₂·6H₂O)?

A

Blue

B

Purple

C

Pink

D

White

19

Anhydrous cobalt chloride (blue) turns into cobalt chloride dihydrate when it absorbs limited moisture. What is the color of the dihydrate?

A

Pink

B

Blue

C

White

D

Purple

20

In a reversible reaction, if one of the products is withdrawn from the reaction mixture, the reaction is?

A

stopped

B

slowed down

C

forced to go to completion

D

unaffected

21

Which of the following is an example of an irreversible reaction?

A

N₂(g) + 3H₂(g) ↔ 2NH₃(g)

B

CaCO₃(s) ↔ CaO(s) + CO₂(g)

C

NaCl(aq) + AgNO₃(aq) → AgCl(s) + NaNO₃(aq)

D

CuSO₄·5H₂O(s) ↔ CuSO₄(s) + 5H₂O(g)

22

The state of equilibrium where the reaction keeps on going in both directions is called?

A

Static equilibrium

B

Completion

C

Irreversible state

D

Dynamic equilibrium

23

In the reaction PCl₅(g) ↔ PCl₃(g) + Cl₂(g), what will happen if the gas mixture is compressed?

A

Equilibrium shifts to the right

B

Equilibrium shifts to the left

C

No change occurs

D

The reaction stops

24

What happens if we add more Cl₂ gas to the equilibrium mixture of PCl₅(g) ↔ PCl₃(g) + Cl₂(g)?

A

More PCl₅ is formed

B

More PCl₃ is formed

C

The reaction becomes faster

D

The reaction stops

25

The decomposition of PCl₅ is an endothermic reaction. What happens if the temperature is increased?

A

The forward reaction is favoured

B

The backward reaction is favoured

C

The reaction rate decreases

D

The catalyst becomes inactive

26

What condition should be met for a reversible reaction to achieve equilibrium?

A

All reactants are converted to products

B

50% of reactants are converted to products

C

The concentration of all species becomes constant

D

A product is removed

27

Ammonia gas is used industrially to produce which important fertilizer?

A

Potassium nitrate

B

Superphosphate

C

Urea

D

Ammonium sulphate

28

If the rates of forward and reverse reactions are very high, the equilibrium point will be reached?

A

very soon

B

very late

C

never

D

only with a catalyst

29

The reaction N₂(g) + O₂(g) ↔ 2NO(g) involves equal moles of gaseous reactants and products. What is the effect of increasing pressure?

A

Forward reaction is favoured

B

Backward reaction is favoured

C

No effect on equilibrium position

D

The reaction stops

30

In the majority of chemical reactions, the reaction does not?

A

produce any product

B

go to completion

C

require heat

D

involve reactants

31

Which of the following is a physical change that is reversible?

A

Burning of wood

B

Rusting of iron

C

Heating of hydrated copper sulphate

D

Digestion of food

32

When white anhydrous copper sulphate absorbs moisture, it will turn?

A

Pink

B

Purple

C

Blue

D

White again

33

A reversible reaction goes to completion if?

A

it is in a closed container

B

the temperature is decreased

C

one of the products is withdrawn

D

a catalyst is added

34

What are the products when dinitrogen tetra oxide (N₂O₄) decomposes at 100°C?

A

N₂ and O₂

B

NO

C

NO₂

D

N₂O

35

What is the color of nitrogen dioxide (NO₂)?

A

Colourless

B

Brown

C

Blue

D

Pink

36

How is ethyl acetate commercially important?

A

As a fertilizer

B

As a fuel

C

As a thinner in paint industry

D

As a food preservative

37

What happens to the solubility of a gas in a fizzy drink when the can is opened?

A

It increases

B

It decreases because pressure is decreased

C

It remains the same

D

It decreases because temperature increases

38

The formation of ammonia is favoured at?

A

low pressure

B

high pressure

C

low temperature only

D

high pressure and high temperature

39

According to the text, the reaction to form ethyl acetate can yield more product if?

A

more alcohol is added

B

more acid is added

C

water is removed as it is formed

D

the temperature is lowered

40

In the reaction 2H₂O(g) ↔ 2H₂(g) + O₂(g), what drives the reaction?

A

Heat

B

Catalyst

C

Pressure

D

Electric current

41

Why are combustion reactions generally irreversible?

A

They are very slow

B

They produce gaseous products that escape

C

They are endothermic

D

They occur in closed containers

42

Which statement is true about a reversible reaction at equilibrium?

A

The reaction has stopped

B

The concentrations of reactants and products are equal

C

The rates of forward and reverse reactions are equal

D

All reactants have been consumed

43

What is the physical state of AgCl formed in the reaction between NaCl(aq) and AgNO₃(aq)?

A

Gas (g)

B

Aqueous (aq)

C

Solid (s)

D

Liquid (l)

44

The decomposition of lime (CaCO₃) is an exothermic reversible reaction. To produce maximum lime, you should?

A

Heat at high temperature in a closed vessel

B

Heat at high temperature in an open vessel

C

Cool it in a closed vessel

D

Cool it in an open vessel

45

If a reversible reaction at equilibrium is not disturbed, the concentrations of the products will?

A

remain constant

B

keep on increasing

C

keep on decreasing

D

become zero

46

What is the total number of moles of reacting gases in the synthesis of ammonia (N₂ + 3H₂ ↔ 2NH₃)?

A

2 moles

B

3 moles

C

4 moles

D

1 mole

47

What is the total number of moles of product gas in the synthesis of ammonia (N₂ + 3H₂ ↔ 2NH₃)?

A

1 mole

B

2 moles

C

3 moles

D

4 moles

48

A reversible reaction may be forced to completion if one or all products are?

A

added to the mixture

B

heated to a high temperature

C

withdrawn from the mixture

D

kept in the mixture

49

When are reversible reactions useful for preparing compounds on a large scale?

A

When equilibrium lies far to the left

B

When equilibrium lies far to the right

C

Never

D

Always