Essential Chemistry for IGCSE - Chemical Changes (Section 1)
1
What is the key feature that distinguishes a chemical change from a physical change?
پاسخ دهید(C)
Formation of new substances.
2
In a simple electrochemical cell, the electrode with the more positive reduction potential will act as the:
3
Which of the following are key features of fuel cells?
4
What do all batteries have in common?
پاسخ دهید(B)
They all have a positive and negative terminal.
5
Which of the following are fuels?
6
What component is essential for any electrochemical cell to function?
7
What does the sign of ΔH (enthalpy change) indicate?
پاسخ دهید(C)
Whether the reaction is endothermic or exothermic
8
Which aspects are advantages of using fuel cells?
9
پاسخ دهید(B)
A device that converts chemical energy directly into electrical energy.
10
Which of the following are forms of fuel that can be used in a fuel cell?
11
What happens to electrons in a fuel cell?
پاسخ دهید(C)
They flow from the anode to the cathode through an external circuit.
12
Which of the following best describes the products of a fuel cell using hydrogen and oxygen?
13
What is the main difference between a physical change and a chemical change?
پاسخ دهید(A)
Physical changes involve a change in state only, while chemical changes involve the formation of new substances.
14
What type of reaction is represented by the following equation: 2H₂ + O₂ -> 2H₂O + energy?
15
Which type of reaction involves the breaking and forming of bonds?
16
What are the main components of a simple electrochemical cell?
17
What is the function of the electrolyte in an electrochemical cell?
پاسخ دهید(B)
To conduct electricity by allowing the flow of ions.
18
In a hydrogen fuel cell, what is produced at the anode?
19
Which type of reaction is characterized by the absorption of energy from the surroundings?
20
What is the role of the platinum in a hydrogen fuel cell?
پاسخ دهید(C)
To catalyze the reactions.
21
What is the purpose of a catalyst in a chemical reaction?
پاسخ دهید(C)
To lower the activation energy of the reaction.
22
Which of the following is an example of a physical change?
23
Which of the following statements best describes an endothermic reaction?
پاسخ دهید(C)
It absorbs energy from the surroundings.
24
Which of the following statements is true about the reactivity series?
پاسخ دهید(D)
The reactivity series helps predict whether a metal will displace another metal.
25
What is the main function of a catalyst?
پاسخ دهید(C)
To speed up the reaction by lowering the activation energy
26
Which statement accurately describes the energy levels in an endothermic reaction?
پاسخ دهید(A)
The products have more energy than the reactants.
27
What is the role of the external circuit in a fuel cell?
پاسخ دهید(B)
To allow the flow of electrons, generating electricity.
28
What is the significance of the negative sign for an energy change (ΔH) in a chemical reaction?
پاسخ دهید(B)
The reaction is exothermic.
29
Which of the following is true regarding endothermic reactions?
30
In a simple electrochemical cell, what is the role of the metal electrodes?
پاسخ دهید(B)
To allow electron flow and be the site of reactions.
31
What type of energy is directly converted into electricity in a fuel cell?
32
Which type of reaction is the burning of a fuel in oxygen?
33
What is a common byproduct of a hydrogen fuel cell?
34
In an electrochemical cell, where does reduction occur?
35
What is the function of the electrolyte in a fuel cell?
پاسخ دهید(C)
To allow the flow of ions between electrodes.
36
What is the role of the platinum electrode in a hydrogen fuel cell?
پاسخ دهید(C)
To catalyze the oxidation of hydrogen and reduction of oxygen.
37
Which of the following is an example of a fuel that can be used in a fuel cell?
38
What is the function of the anode in a fuel cell?
39
What is the purpose of the salt bridge in an electrochemical cell?
پاسخ دهید(B)
To maintain electrical neutrality in the half-cells.
40
Which of the following correctly represents a chemical reaction?
41
Which of the following is an example of an exothermic reaction?
42
What is the role of hydrogen gas in a fuel cell?
43
Which type of reaction is often characterized by an increase in temperature?
44
Which process involves the formation of a new substance?
45
Which of the following correctly represents an exothermic reaction?
پاسخ دهید(B)
Reactants -> Products + Heat
46
What is the general rule of thumb concerning the reactivity series of metals?
پاسخ دهید(B)
The higher the metal is on the reactivity series the greater its tendency to release electrons.
47
What is the source of electricity in a hydrogen fuel cell?
پاسخ دهید(C)
The flow of electrons through an external circuit.
48
In a fuel cell, where does the reduction of oxygen occur?
49
What is the primary purpose of a catalyst?
پاسخ دهید(C)
To speed up the reaction rate.
50
Which of the following is NOT a characteristic of an exothermic reaction?
پاسخ دهید(D)
The reaction absorbs heat from the surroundings.
