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Essential Chemistry for IGCSE - Chemical Reactions (Section 1)

1
Which of the following species acts as the oxidizing agent in the following reaction? 2Mg(s) + O2(g) -> 2MgO(s)
Answer
(B)
O2
2
What is the effect of adding an inert gas to an equilibrium mixture at constant volume?
Answer
(C)
The equilibrium remains unchanged.
3
Which of the following is the reducing agent in the reaction: CuO(s) + H2(g) → Cu(s) + H2O(g)?
Answer
(B)
H2
4
Which of the following statements is/are true about an equilibrium that is established in a closed system?
Answer
A
B
5
In a closed system at equilibrium, what remains constant?
Answer
(D)
All of the above.
6
What is the meaning of the term "equilibrium constant"?
Answer
(B)
The ratio of products to reactants at equilibrium.
7
Which of the following statements is the best description of the term 'redox reaction'?
Answer
(B)
A reaction involving the transfer of electrons.
8
In a redox reaction, the species that gains electrons is said to be:
Answer
(B)
Reduced
9
In the reaction: 2Mg(s) + O2(g) -> 2MgO(s), what is the role of oxygen?
Answer
(B)
Oxidizing agent
10
In the Haber process (N2(g) + 3H2(g) ⇌ 2NH3(g)), what effect does increasing the pressure have on the yield of ammonia?
Answer
(B)
Increases the yield.
11
What is the role of hydrogen (H2) in the following reaction: CuO(s) + H2(g) → Cu(s) + H2O(g)?
Answer
(A)
Reducing agent
12
If a reaction is exothermic, which of the following statements is true?
Answer
(D)
Heat is released to the surroundings.
13
Which of the following will increase the yield of products in an exothermic reaction?
Answer
B
C
14
Which of the following is true about the reaction: H2(g) + I2(g) ⇌ 2HI(g) ΔH > 0?
Answer
(B)
Increasing the temperature favors the production of HI.
15
Which of the following is reduced in the reaction: 2Na + Cl2 → 2NaCl?
Answer
(B)
Cl2
16
What does the term 'equilibrium' in a chemical reaction imply?
Answer
(C)
The rates of the forward and reverse reactions are equal.
17
Which of the following is true concerning catalysts?
Answer
(C)
Catalysts speed up a reaction by providing an alternative reaction pathway.
18
Which of the following best describes the process of reduction?
Answer
(C)
Gain of electrons.
19
In the reaction: Fe³⁺(aq) + Cu(s) → Fe²⁺(aq) + Cu²⁺(aq), which species is the reducing agent?
Answer
(B)
Cu
20
Which of the following statements is/are TRUE concerning a chemical reaction at equilibrium?
Answer
A
B
21
Consider the reaction: CH4(g) + 2O2(g) ⇌ CO2(g) + 2H2O(g) ΔH < 0. What would happen if you remove some of the water vapor?
Answer
(B)
The equilibrium shifts to the right.
22
Which of the following is/are true about the impact of pressure changes on a reversible reaction?
Answer
B
C
23
What is a defining feature of a system at equilibrium?
Answer
A
B
24
Which of the following statements regarding Le Chatelier's principle is/are correct?
Answer
A
C
D
25
What is the oxidation state of oxygen in most compounds?
Answer
(C)
-2
26
What will happen when cobalt chloride is added to water?
Answer
(C)
The solution will change to pink
27
Which of the following will increase the rate of a chemical reaction?
Answer
A
B
C
D
28
What happens to the equilibrium position when a product is removed from the reaction mixture?
Answer
(B)
The equilibrium shifts to favor the reactants.
29
Which of the following is/are characteristic of a chemical reaction at equilibrium?
Answer
A
B
D
30
Which of the following statements is correct regarding endothermic reactions?
Answer
(C)
The products have higher energy than the reactants.
31
Which of the following is true of an exothermic reaction?
Answer
(D)
It is favored by a decrease in temperature.
32
In the reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g) ΔH < 0, which of the following conditions would favor the production of SO3?
Answer
A
D
33
In the reaction: Fe²⁺(aq) + Cr₂O₇²⁻(aq) → Fe³⁺(aq) + Cr³⁺(aq) (unbalanced). What is being reduced?
Answer
(B)
Cr₂O₇²⁻
34
Consider the reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g) ΔH < 0. What effect will decreasing the temperature have on the equilibrium?
Answer
(B)
Shift the equilibrium to the right.
35
Which of the following conditions will favor an exothermic reaction?
Answer
B
C
36
What is the purpose of using a catalyst in a chemical reaction?
Answer
(C)
To increase the reaction rate.
37
What is the key difference between oxidation and reduction in terms of electron transfer?
Answer
(B)
Reduction involves the gain of electrons, oxidation involves the loss.
38
Which of the following factors can change the equilibrium constant (K) of a reversible reaction?
Answer
(D)
Changing the temperature.
39
What effect does a catalyst have on the equilibrium position of a reversible reaction?
Answer
(C)
Does not affect the equilibrium position.
40
Which of the following processes involves a decrease in oxidation number?
Answer
(B)
Reduction
41
In the reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g), if more O2 is added to the system, what will happen?
Answer
(B)
The equilibrium will shift to the right.
42
For the reaction: A(g) + B(g) ⇌ C(g) + heat, which of the following would shift the equilibrium to the right?
Answer
(B)
Decreasing the temperature.
43
Which of the following describes a reversible reaction?
Answer
(B)
A reaction that can be reversed by changing the conditions.
44
Which of the following statements is true about the Haber process: N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH < 0?
Answer
(B)
Decreasing the temperature favors the production of ammonia.
45
What is the effect of increasing the temperature on an exothermic reaction at equilibrium?
Answer
(B)
The equilibrium shifts to favor the reactants.
46
What is the reducing agent in the following reaction: 2FeCl3 + SnCl2 -> 2FeCl2 + SnCl4
Answer
(B)
SnCl2
47
Which of the following is NOT a characteristic of a system at chemical equilibrium?
Answer
(C)
The reaction has stopped.
48
What is the sign of ΔH for an exothermic reaction?
Answer
(B)
Negative
49
Which of the following is the best definition of oxidation?
Answer
(C)
The gain of oxygen.
50
Which of the following will increase the rate of a chemical reaction?
Answer
A
B
D