Energy Changes Practice Questions
WAEC (West Africa) · WAEC Chemistry · 148 free MCQs with instant results and detailed explanations.
148
Total
45
Easy
76
Medium
27
Hard
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Sample Questions from Energy Changes
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Q1
Easy
What is the term for the energy required to break the bonds in reactants during a chemical reaction?
A.
Activation energy
B.
Kinetic energy
C.
Potential energy
D.
Thermal energy
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Correct Answer: A
Activation energy is the minimum energy required to break chemical bonds in reactants, allowing a reaction to occur. This concept is crucial in understanding how reactions proceed.
Q2
Easy
During an exothermic reaction, what happens to the energy of the system?
A.
Energy is absorbed from the surroundings.
B.
Energy is released to the surroundings.
C.
Energy remains constant.
D.
Energy is converted into mass.
Show Answer & Explanation
Correct Answer: B
In an exothermic reaction, the system releases energy, usually in the form of heat, to the surroundings. This results in a decrease in the internal energy of the system.
Q3
Easy
Which of the following processes is an example of an endothermic reaction?
A.
Burning of wood
B.
Dissolving ammonium nitrate in water
C.
Respiration in living organisms
D.
Combustion of fuels
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Correct Answer: B
Dissolving ammonium nitrate in water is an endothermic process because it absorbs heat from the surroundings, resulting in a temperature drop of the solution.
Q4
Medium
Which of the following processes is an example of an endothermic reaction?
A.
Dissolving ammonium nitrate in water
B.
Combustion of hydrocarbons
C.
Formation of water from hydrogen and oxygen
D.
Neutralization of an acid with a base
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Correct Answer: A
Dissolving ammonium nitrate in water absorbs heat, thus it is an endothermic process, where the surroundings get cooler.
Q5
Medium
Which statement best describes an exothermic reaction?
A.
It absorbs heat from the surroundings.
B.
It releases heat to the surroundings.
C.
It has no energy change.
D.
It requires continuous energy input.
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Correct Answer: B
An exothermic reaction is characterized by the release of heat to the surroundings, making the surrounding environment warmer.
Q6
Medium
In a chemical reaction, the enthalpy change (ΔH) is -150 kJ/mol. What type of reaction is this?
A.
Exothermic
B.
Endothermic
C.
Isothermal
D.
Isobaric
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Correct Answer: A
A negative enthalpy change indicates that the reaction releases heat, defining it as exothermic.
Q7
Medium
When 50 grams of sodium hydroxide (NaOH) is dissolved in water, the temperature of the solution rises. What does this indicate about the dissolution process?
A.
It is exothermic.
B.
It is endothermic.
C.
It reaches thermal equilibrium.
D.
It absorbs moisture from the air.
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Correct Answer: A
The rise in temperature indicates that heat is released during the dissolution of sodium hydroxide, confirming it as an exothermic process.
Q8
Hard
In an exothermic reaction, which of the following statements is correct regarding the energy changes involved?
A.
Energy is absorbed from the surroundings.
B.
The enthalpy of products is higher than that of reactants.
C.
Heat is released to the surroundings.
D.
The reaction occurs at constant pressure only.
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Correct Answer: C
In an exothermic reaction, energy is released in the form of heat to the surroundings, resulting in a decrease in the enthalpy of the system. This is why option C is correct.
Q9
Hard
During an endothermic reaction, which of the following statements is true regarding the energy changes involved?
A.
The system releases heat to the surroundings.
B.
The energy of the products is lower than that of the reactants.
C.
The system absorbs heat from the surroundings.
D.
The reaction occurs spontaneously without energy input.
Show Answer & Explanation
Correct Answer: C
In an endothermic reaction, the system absorbs heat from the surroundings, resulting in a gain of energy. This makes option C correct, as the products will generally have higher energy than the reactants.
Q10
Hard
A student measures the temperature change when a certain amount of 0.5 mol/L hydrochloric acid is mixed with 0.5 mol/L sodium hydroxide. If the temperature increases by 5°C, what type of reaction is occurring?
A.
Endothermic reaction.
B.
Exothermic reaction.
C.
No reaction occurs.
D.
Thermochemical reaction.
Show Answer & Explanation
Correct Answer: B
The increase in temperature indicates that heat is being released into the surroundings, which is characteristic of an exothermic reaction. Therefore, option B is correct.
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Energy Changes — WAEC (West Africa) WAEC Chemistry Practice Questions Online
This page contains 148 practice MCQs for the chapter Energy Changes in WAEC (West Africa) WAEC Chemistry. The questions are organized by difficulty — 45 easy, 76 medium, 27 hard — so you can choose the right level for your preparation.
Every question includes a detailed explanation to help you understand the concept, not just memorize answers. Take a timed quiz to simulate exam conditions, or practice at your own pace with no time limit.