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Essential Chemistry for IGCSE - Chemical Reactions (Section 2)

1
What does the Haber process produce?
Answer
(A)
Ammonia
2
How does a catalyst affect the equilibrium of a reversible reaction?
Answer
(C)
It increases the rate of both the forward and reverse reactions equally.
3
At equilibrium, what is the relationship between the forward and reverse reaction rates?
Answer
(C)
The rates are equal.
4
Consider the following reaction: 2NO(g) + O2(g) ⇌ 2NO2(g) ΔH < 0. What effect will increasing the temperature have on the equilibrium?
Answer
(B)
Shift the equilibrium to the left (favoring the reactants).
5
In a redox reaction, the substance that loses electrons is:
Answer
(A)
Oxidized
6
In the reversible reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g), which of the following statements is/are correct regarding a decrease in volume?
Answer
A
C
7
Which of the following statements about redox reactions is true?
Answer
(C)
Oxidation and reduction always occur simultaneously.
8
Which of the following is the reducing agent in the reaction: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)?
Answer
(A)
Zn
9
What is a characteristic of a system at chemical equilibrium?
Answer
(B)
The forward and reverse reactions are occurring at the same rate.
10
Consider the reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g) ΔH = -198 kJ/mol. Which conditions favor the formation of SO3?
Answer
(D)
Decreasing the temperature and increasing the pressure.
11
Which of the following describes a system at dynamic equilibrium?
Answer
(B)
The concentrations of reactants and products are constant.
12
What are the essential conditions for a reversible reaction to reach equilibrium?
Answer
A
B
D
13
Which of the following statements is/are correct regarding the role of a catalyst in a chemical reaction?
Answer
B
C
14
In a redox reaction, which of the following always occurs?
Answer
(C)
The transfer of electrons.
15
Which of the following is the best definition of oxidation?
Answer
(B)
The loss of electrons
16
In a reversible reaction at equilibrium, how does a catalyst affect the rate?
Answer
(C)
Increases both the forward and reverse rates.
17
Which of the following statements are true about oxidation states?
Answer
A
B
D
18
What are the key characteristics of a system that has reached equilibrium?
Answer
(C)
The rate of the forward reaction equals the rate of the reverse reaction.
19
If the forward reaction in a reversible reaction is exothermic, what is true about the reverse reaction?
Answer
(B)
It is endothermic.
20
Which of the following statements describes chemical equilibrium?
Answer
(B)
The rate of the forward reaction equals the rate of the reverse reaction.
21
Which of the following is the best description of Le Chatelier's principle?
Answer
(B)
The equilibrium shifts to relieve stress.
22
Which of the following statements correctly describes oxidation?
Answer
(B)
It is the loss of electrons by a substance.
23
What is the role of the reducing agent in a redox reaction?
Answer
(A)
It is oxidized.
24
Which of the following processes/reactions involve a change in oxidation number?
Answer
A
D
25
In general, how does increasing the temperature affect the rate of a chemical reaction?
Answer
(B)
Increases the rate.
26
Which of the following is/are factors that can affect the position of equilibrium in a reversible reaction?
Answer
A
B
C
27
Which of the following statements correctly describes the roles of the oxidizing and reducing agents in a redox reaction?
Answer
C
D
28
Which of the following is the definition of oxidation number?
Answer
(B)
The hypothetical charge an atom would have if all bonds were ionic.
29
What is the oxidizing agent in the reaction: Cu(s) + 2Ag+(aq) → Cu²⁺(aq) + 2Ag(s)?
Answer
(B)
Ag+(aq)
30
Which of the following best defines an oxidizing agent?
Answer
(B)
A substance that gains electrons in a reaction.
31
What is the oxidation state of chlorine in the compound HClO?
Answer
(C)
+1
32
Which of the following factors affects the position of equilibrium?
Answer
(B)
Changing the volume of the container.
33
What is the sign of the enthalpy change (ΔH) for an endothermic reaction?
Answer
(A)
Positive
34
If a reaction has a negative enthalpy change (ΔH < 0), what type of reaction is it?
Answer
(A)
Exothermic
35
In the reaction: Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s), which species is the oxidizing agent?
Answer
(B)
Cu²⁺
36
What are characteristics of a chemical reaction at equilibrium?
Answer
A
B
D
37
In the following reaction, what will happen if the concentration of Cl2 is increased? H2(g) + Cl2(g) ⇌ 2HCl(g)
Answer
(B)
The equilibrium shifts to the right.
38
Which of the following is the correct definition of an equilibrium?
Answer
(C)
The rate of the forward reaction is equal to the rate of the reverse reaction.
39
Which of the following statements are TRUE regarding the characteristics of a catalyst?
Answer
A
C
40
What is the relationship between the rate of the forward reaction and the reverse reaction at equilibrium?
Answer
(C)
The rates are equal.
41
What is the effect of adding a catalyst to a reversible reaction?
Answer
(B)
The reaction rate increases, but the equilibrium position does not change.
42
In the reaction 2CO(g) + O2(g) ⇌ 2CO2(g), if the concentration of CO2 is increased, what happens to the equilibrium?
Answer
(A)
Equilibrium shifts to the left.
43
What does it mean for a reaction to be at equilibrium?
Answer
(B)
The forward and reverse reactions are occurring at the same rate.
44
Which of the following statements is/are true regarding Le Chatelier's principle?
Answer
A
C
D
45
Which of the following is true regarding the reaction between copper(II) oxide and hydrogen?
Answer
(C)
Copper(II) oxide is reduced, and hydrogen is the reducing agent.
46
Which of the following is/are true regarding endothermic reactions?
Answer
A
B
C
47
Which of the following will change the value of the equilibrium constant, K?
Answer
(D)
Changing the temperature.
48
In the reaction: 2H2(g) + O2(g) ⇌ 2H2O(g), which condition favors the production of water (H2O)?
Answer
(A)
Increasing the pressure.
49
Which of the following changes *does* affect the value of the equilibrium constant (K)?
Answer
(C)
Changing the temperature
50
For the reaction: A(g) + B(g) ⇌ C(g) + D(g). If the pressure is increased, the equilibrium will:
Answer
(B)
Shift to the side with fewer moles of gas.