Chemical Reactions Test

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Chemical Reactions Test - 1

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Weekly Quiz Competition

Question 1
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Which of the following statements are true regarding a catalyst?

I. It is a substance which increases the rate of the reaction.
II. It is a substance which reduces the activation energy.
III. It is a substance which increases the activation energy.
IV. It is a substance which is consumed in the reaction.

A
I and II

B
II and III

C
III and IV

D
I and IV

Solution

Catalyst is a substance which increases the rate of a reaction and reduces the activation energy of the reaction by providing a new pathway to the reaction.

A catalyst is never consumed during the reaction and is always regenerated in the end.
Question 2
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Which of the following options is true for all chemical reactions?

A
Heat is evolved.

B
There is a change in volume.

C
Chemical bonds are broken or formed.

D
There is a change in mass.

Solution

Chemical bonds are broken or formed. From the given options, this is true for all chemical reactions.
Question 3
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In the synthesis of NH₃ from N₂ and H₂, Fe and Mo (Molybdenum) are used to alter the speed of the reaction. In this process, Mo acts as

A
a catalyst

B
a negative catalyst

C
a promoter

D
an auto catalyst

Solution

In the synthesis of NH₃ from N₂ and H₂, Fe and Mo are used to alter the speed of the reaction. In this process, Mo acts as a promoter.

A promoter, is a substance added to a solid catalyst to improve its performance in a chemical reaction.
Question 4
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Which of the following best explains the action of a catalyst in enhancing the rate of a chemical reaction?

A
It decreases the energy of activation of the reaction.

B
It prevents the reverse reaction from occurring.

C
It increases the value of equilibrium constant of the reaction.

D
It increases the kinetic energy of the molecules.

Solution

Catalyst decreases the energy of activation of the reaction, which enhances the rate of a chemical reaction.

Both kinetic energy and equilibrium constant are a function of the temperature and are not affected by the addition of the catalyst.
Question 5
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Oxygen is liberated on heating

A
zinc oxide

B
manganese dioxide

C
mercuric oxide

D
magnesium oxide

Solution

Oxygen is liberated on heating mercuric oxide.
HgO is an unstable oxide and breaks down on heating to liberate free oxygen.
2HgO(s) + heat ---> 2Hg(l) + O₂(g)
Question 6
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Which of the following options is incorrect about oxidation?

A
Addition of an electronegative element

B
Increase of positive valence

C
Gain of electrons

D
Removal of hydrogen

Solution

Oxidation is the process of loss of electrons.
Question 7
1 / -0

Which of the following can be considered as a weak electrolyte?

A
NaCI

B
HCI

C
CH₃COOH

D
K₂SO₄

Solution

Acetic acid (CH₃COOH) is considered as a weak electrolyte because it dissociates partially in its aqueous solution to form ions.
Question 8
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Which of the following are redox reactions?

I. Cu + 2H₂SO₄→ CuSO₄ + 2H₂O + SO₂

II. BaCI₂ + H₂SO₄→ BaSO₄ + 2HCI

III. Zn + H₂SO₄→ ZnSO₄ + H₂

IV. 2KNO₃ + H₂SO₄→2HNO₃ + K₂SO₄

A
II and IV only

B
I, II and III only

C
I and III only

D
I and IV only

Solution

Reactions I and III are redox reactions.

In reaction I, Cu is getting oxidised (oxidation state changes from 0 to +2) and S is getting reduced (oxidation state changes from +6 to +4).

In reaction III, Zn is getting oxidised (oxidation state changes from 0 to +2) and H⁺ is getting reduced (oxidation state changes from +1 to 0).

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Chemical Reactions Test - 1

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Question 1

I and II

II and III

III and IV

I and IV

Solution

Question 2

Heat is evolved.

There is a change in volume.

Chemical bonds are broken or formed.

There is a change in mass.

Solution

Question 3

a catalyst

a negative catalyst

a promoter

an auto catalyst

Solution

Question 4

It decreases the energy of activation of the reaction.

It prevents the reverse reaction from occurring.

It increases the value of equilibrium constant of the reaction.

It increases the kinetic energy of the molecules.

Solution

Question 5

zinc oxide

manganese dioxide

mercuric oxide

magnesium oxide

Solution

Question 6

Addition of an electronegative element

Increase of positive valence

Gain of electrons

Removal of hydrogen

Solution

Question 7

NaCI

HCI

CH3COOH

K2SO4

Solution

Question 8

II and IV only

I, II and III only

I and III only

I and IV only

Solution

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CH₃COOH

K₂SO₄