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Essential Chemistry for IGCSE - Chemical Changes (Section 2)

1
What is the purpose of the electrolyte in an electrochemical cell?
Answer
(A)
To allow the flow of ions.
2
In a fuel cell, how does the hydrogen react at the negative electrode (anode) in an alkaline electrolyte?
Answer
(A)
H₂ + 2OH⁻ -> 2H₂O + 2e⁻
3
What does 'H' represent in energy level diagrams?
Answer
(B)
Enthalpy
4
What is a chemical change?
Answer
(C)
The formation of a new substance.
5
In a hydrogen fuel cell, what happens at the cathode?
Answer
(B)
Oxygen molecules are reduced.
6
What is the oxidation number of an atom in its elemental form?
Answer
(C)
0
7
What is the main advantage of using fuel cells?
Answer
(C)
They produce only water as a byproduct.
8
Which of the following are advantages of a fuel cell?
Answer
A
C
9
What does the difference between the energy of the reactants and the products represent?
Answer
(B)
Enthalpy change (ΔH)
10
What happens to the electrodes in an electrochemical cell as the cell runs?
Answer
(C)
The electrodes lose mass.
11
Which of the following is an example of a chemical change?
Answer
(C)
Burning paper
12
What does the 'activation energy' represent in a chemical reaction?
Answer
(B)
The minimum energy required for the reaction to start.
13
Which electrode is the site of oxidation in an electrochemical cell?
Answer
(A)
Anode
14
Which of the following is a characteristic of an exothermic reaction?
Answer
(C)
The temperature of the surroundings increases.
15
A reaction is exothermic if:
Answer
(C)
The reaction releases heat to the surroundings.
16
What is the function of the salt bridge in a galvanic cell?
Answer
(C)
To maintain charge balance in the half-cells.
17
Which of the following statements about the reactivity series is correct?
Answer
(A)
Metals higher in the series readily lose electrons.
18
Which of the following is true for an exothermic reaction?
Answer
A
B
D
19
Which of the following is a characteristic of a chemical change?
Answer
(C)
Formation of a new substance
20
What does the term 'bond energy' refer to?
Answer
(A)
The energy required to break one mole of a particular bond in one mole of gaseous atoms.
21
What is the role of a metal in an electrochemical cell?
Answer
A
C
22
What is the primary difference between an electrolytic cell and a fuel cell?
Answer
(A)
Electrolytic cells use electricity to drive chemical reactions, while fuel cells generate electricity from chemical reactions.
23
What is the main advantage of fuel cells over internal combustion engines?
Answer
(C)
They are more efficient and produce fewer emissions.
24
What is the main energy source used in a nuclear power station?
Answer
(B)
Uranium
25
What is the main product of a hydrogen fuel cell?
Answer
(C)
Water
26
What happens to energy during a physical change?
Answer
(D)
Energy may be absorbed or released.
27
In a simple electrochemical cell, which electrode is the site of oxidation?
Answer
(B)
The anode
28
Which of the following is not a product of a hydrogen fuel cell reaction?
Answer
(D)
Carbon Dioxide
29
In a hydrogen fuel cell, which electrode is the cathode, and what reaction occurs there?
Answer
(D)
Cathode, oxygen reduction
30
In a simple electrochemical cell, what direction do electrons flow?
Answer
(C)
From the anode to the cathode.
31
In a hydrogen fuel cell, which ion is the charge carrier in the acidic electrolyte?
Answer
(C)
Hydrogen (H⁺)
32
Which of the following is the primary function of a battery?
Answer
(C)
To store and release electrical energy.
33
In a hydrogen fuel cell, which material is typically used as the electrolyte?
Answer
(B)
Aqueous solution of acid or alkali
34
In the context of fuel cells, what is the role of a catalyst?
Answer
A
C
35
What do all electrochemical cells have in common?
Answer
(A)
They involve oxidation and reduction reactions.
36
In a fuel cell, the reaction at the anode is:
Answer
(B)
Oxidation of hydrogen.
37
What is the standard unit for bond energy?
Answer
(C)
Kilojoules per mole (kJ/mol)
38
What is a key feature of a fuel cell compared to a combustion engine?
Answer
A
C
39
What is the role of oxygen in a fuel cell?
Answer
(B)
It is the oxidizing agent.
40
What is the relationship between potential difference and electrochemical reactions?
Answer
A
D
41
What type of energy is primarily converted into electrical energy in a fuel cell?
Answer
(B)
Chemical energy
42
Which of the following statements are correct about the comparison of chemical changes and physical changes?
Answer
A
C
D
43
In a simple electrochemical cell, which electrode is the site of reduction?
Answer
(B)
Cathode
44
If a reaction is endothermic, what can be said about the energy of the products versus the reactants?
Answer
(C)
The products have more energy.
45
Which of the following is a characteristic of an acidic electrolyte in a fuel cell?
Answer
(A)
The hydrogen ions move through the electrolyte.
46
What is the function of the electrodes in an electrochemical cell?
Answer
(C)
To be the site of oxidation and reduction reactions.
47
What is a fuel?
Answer
(B)
A substance that releases energy when it burns.
48
If a reaction has a positive enthalpy change (ΔH), what type of reaction is it?
Answer
(B)
Endothermic
49
In a chemical reaction, if the energy of the reactants is higher than the energy of the products, what type of reaction is it?
Answer
(A)
Exothermic
50
What are the main reactants in a hydrogen fuel cell?
Answer
(A)
Hydrogen and oxygen