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Essential Chemistry for IGCSE - Chemical Reactions (Section 6)

1
In a chemical reaction, what is the function of a catalyst?
Answer
(C)
To provide an alternative reaction pathway with a lower activation energy.
2
What color change occurs when potassium permanganate solution reacts with a reducing agent?
Answer
(B)
Purple to colorless
3
What is the meaning of 'reversible reaction'?
Answer
(C)
A reaction that can proceed in both forward and reverse directions.
4
If a reaction at equilibrium has a high concentration of reactants, what will happen if you add more reactants?
Answer
(B)
The equilibrium will shift to the right.
5
Which of the following describes a characteristic of a chemical reaction at equilibrium?
Answer
(C)
The rate of the forward reaction equals the rate of the reverse reaction.
6
For the reaction: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), if more O₂ is added, what happens?
Answer
(B)
The equilibrium shifts to the right.
7
Which of the following is true for an exothermic reaction?
Answer
A
B
C
D
8
What is reduction in terms of electron transfer?
Answer
(A)
Gain of electrons
9
What is the oxidation number of chlorine in HClO₃?
Answer
(C)
+5
10
What is the role of the reducing agent in a redox reaction?
Answer
(D)
Both B and C.
11
What will happen to the equilibrium if a catalyst is added to the reaction?
Answer
(C)
The equilibrium position will not change, but the rate of reaction will increase.
12
What is the role of a reducing agent in a redox reaction?
Answer
(D)
To cause reduction.
13
What does the term 'dynamic equilibrium' mean in a reversible reaction?
Answer
(C)
The rate of the forward reaction equals the rate of the reverse reaction.
14
What is the oxidation state of oxygen in a peroxide (e.g., H₂O₂)?
Answer
(B)
-1
15
Which change will shift the equilibrium to the right for the reaction: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) ΔH < 0
Answer
B
D
16
What is the function of the reducing agent?
Answer
(B)
To donate electrons and be oxidized