Essential Chemistry for IGCSE - Chemical Reactions (Section 3)
1
Consider the following reversible reaction: N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH < 0. Which of the following will increase the yield of ammonia?
Answer
(D)
Increasing the concentration of nitrogen.
2
What will be the effect of decreasing the pressure on the following reaction? 2SO2(g) + O2(g) ⇌ 2SO3(g)
Answer
(B)
The equilibrium shifts to the left.
3
What is the effect of increasing the pressure on the following equilibrium: 2NO2(g) ⇌ N2O4(g)?
Answer
(B)
The equilibrium shifts to the right.
4
What is the sign of ΔH for an exothermic reaction?
Answer
(B)
Negative
5
What does the term 'equilibrium' mean in the context of a chemical reaction?
Answer
(C)
The rate of the forward reaction equals the rate of the reverse reaction.
6
In a reversible reaction at equilibrium, which of the following statements is correct?
Answer
(C)
The rates of the forward and reverse reactions are equal.
7
What is a characteristic of the oxidizing agent in a redox reaction?
Answer
(C)
It is reduced in the reaction.
8
Which of the following statements are true about a system at equilibrium?
Answer
B
C
9
In the reaction: 2NO(g) + O2(g) ⇌ 2NO2(g), the equilibrium shifts to the right if:
Answer
(D)
The pressure is increased.
10
What happens to the equilibrium position when the concentration of reactants is increased?
Answer
(A)
The equilibrium shifts to favor the products.
11
Which of the following is the correct formula for an oxidizing agent?
Answer
(C)
It causes another substance to be oxidized.
12
Which of the following statements is/are true about a reaction that is at equilibrium?
Answer
B
C
13
Which of the following statements correctly describes what happens to the concentration of reactants and products at equilibrium?
Answer
(C)
The concentrations of reactants and products are constant.
14
For the exothermic reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g), which conditions would favor the formation of SO3?
Answer
(B)
Decrease temperature and increase pressure.
15
What is the effect of adding a catalyst to a reversible reaction at equilibrium?
Answer
(C)
It increases the rate of the reaction without changing the equilibrium position.
16
Which of the following is true about catalysts?
Answer
(C)
They lower the activation energy.
17
Which of the following best defines reduction in a redox reaction?
Answer
(A)
The gain of electrons
18
Which of the following statements is/are correct regarding the impact of a catalyst on a reversible reaction?
Answer
A
C
D
19
Which of the following statements is true about the oxidation state of an element in its elemental form (e.g., O2, Na)?
Answer
(C)
It is always 0.
20
What are the essential requirements for a chemical reaction to be considered at equilibrium?
Answer
A
B
D
21
What happens when a reducing agent is added to a solution of acidified potassium permanganate?
Answer
(C)
The solution turns from purple to colorless.
22
For the reaction: A + B ⇌ C + D. If the concentration of A is increased, what will happen?
Answer
(B)
The equilibrium shifts to the right.
23
What is oxidation in terms of electron transfer?
Answer
(B)
Loss of electrons
24
Which of the following statements are true about redox reactions?
Answer
A
B
C
25
Which of the following will increase the rate of a chemical reaction?
Answer
A
B
C
26
Consider the reaction: 2CO(g) + O₂(g) ⇌ 2CO₂(g). If you increase the pressure, what will happen?
Answer
(B)
The equilibrium shifts to the right.
27
What happens to the oxidation number of an element when it undergoes oxidation?
Answer
(C)
It increases.
28
In a redox reaction, the oxidizing agent...
Answer
(B)
gains electrons and is reduced.
29
In the reaction: 2Fe³⁺ + Sn²⁺ → 2Fe²⁺ + Sn⁴⁺, what is being oxidized?
Answer
(B)
Sn²⁺
30
What happens to the oxidation number of an element when it loses electrons?
Answer
(B)
It increases.
31
Which of the following correctly describes what happens during oxidation?
Answer
(C)
Loss of electrons
32
Which of the following can shift the position of an equilibrium?
Answer
A
B
D
33
What is the effect of increasing the concentration of reactants in a reversible reaction?
Answer
(B)
The equilibrium shifts to the right.
34
What type of reaction is required for a compound to decompose?
Answer
(B)
Decomposition
35
Which of the following correctly describes a redox reaction?
Answer
(C)
A reaction where oxidation and reduction occur simultaneously.
36
Which of these conditions generally favors the formation of products in an exothermic reaction?
Answer
(B)
Decreasing the temperature
37
What is the effect of adding a catalyst on a chemical reaction's equilibrium position?
Answer
(C)
The equilibrium position is unchanged.
38
In a reversible reaction at equilibrium, which of the following is TRUE?
Answer
A
B
39
What is the role of the reducing agent in a redox reaction?
Answer
(C)
To donate electrons and be oxidized.
40
In a redox reaction, the substance that is reduced:
Answer
(B)
gains electrons.
41
What is a key characteristic of an equilibrium state?
Answer
(C)
The concentrations of reactants and products are constant.
42
What is the oxidation state of sulfur in sulfuric acid (H₂SO₄)?
Answer
(C)
+6
43
Which of the following is the definition of a reducing agent?
Answer
(B)
A substance that loses electrons.
44
Which of the following reactions would increase the yield of the product when pressure is increased?
Answer
(C)
2NO₂(g) ⇌ N₂O₄(g)
45
What is the effect on the equilibrium of increasing the pressure in a reaction where there are more moles of gas on the reactant side than the product side?
Answer
(A)
Equilibrium shifts to the right.
46
What happens to the equilibrium position if more product is removed from a reaction at equilibrium?
Answer
(B)
Equilibrium shifts to the right.
47
Which factor(s) can affect the rate of a chemical reaction?
Answer
A
B
C
D
48
In the reaction: 2CO(g) + O₂(g) ⇌ 2CO₂(g) ΔH < 0, which of the following changes would shift the equilibrium to the right (favoring the formation of CO₂)?
Answer
(A)
Decreasing the temperature
49
In the Haber process, what is the effect of increasing the pressure on the yield of ammonia?
Answer
(A)
The yield of ammonia increases.
50
Consider the reaction: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) ΔH < 0. If the temperature is increased, what will happen to the equilibrium?
