Chemical Reactions Practice Questions
IGCSE (Cambridge) · IGCSE Chemistry · 145 free MCQs with instant results and detailed explanations.
145
Total
44
Easy
76
Medium
25
Hard
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Sample Questions from Chemical Reactions
Here are 10 sample questions. Start a quiz to get randomized questions with scoring.
Q1
Easy
What type of reaction occurs when magnesium reacts with oxygen to form magnesium oxide?
A.
Synthesis reaction
B.
Decomposition reaction
C.
Single displacement reaction
D.
Double displacement reaction
Show Answer & Explanation
Correct Answer: A
This is a synthesis reaction because two reactants (magnesium and oxygen) combine to form a single product (magnesium oxide).
Q2
Easy
In a chemical reaction, if the mass of the reactants is 50 grams, what will be the mass of the products?
A.
50 grams
B.
45 grams
C.
55 grams
D.
60 grams
Show Answer & Explanation
Correct Answer: A
According to the law of conservation of mass, the mass of the reactants must equal the mass of the products in a chemical reaction, hence it remains 50 grams.
Q3
Easy
Which of the following changes in color indicates a chemical reaction has occurred?
A.
Baking soda dissolving
B.
Iron rusting
C.
Water boiling
D.
Salt dissolving in water
Show Answer & Explanation
Correct Answer: B
Iron rusting involves a chemical change where iron reacts with oxygen and moisture, resulting in a color change due to the formation of iron oxide (rust).
Q4
Medium
What is the main difference between an endothermic and an exothermic reaction?
A.
Endothermic reactions release heat, exothermic absorb heat.
B.
Endothermic reactions absorb heat, exothermic release heat.
C.
Endothermic reactions occur spontaneously, exothermic do not.
D.
Endothermic reactions produce electricity, exothermic do not.
Show Answer & Explanation
Correct Answer: B
Endothermic reactions absorb heat from their surroundings, while exothermic reactions release heat. This is the fundamental distinction between the two types of reactions.
Q5
Medium
Which of the following represents a balanced chemical equation for the reaction of hydrogen and oxygen to form water?
A.
2H2 + O2 → 2H2O
B.
H2 + O2 → H2O
C.
H2 + 2O2 → H2O2
D.
2H2 + 2O2 → 2H2O2
Show Answer & Explanation
Correct Answer: A
The balanced equation is 2H2 + O2 → 2H2O, which shows that two moles of hydrogen react with one mole of oxygen to produce two moles of water, maintaining the law of conservation of mass.
Q6
Medium
In a reaction, if the concentration of a reactant is increased, what is likely to happen to the rate of the reaction?
A.
The rate will decrease.
B.
The rate will remain constant.
C.
The rate will increase.
D.
The rate will become unpredictable.
Show Answer & Explanation
Correct Answer: C
Increasing the concentration of a reactant generally increases the rate of a reaction because it leads to more frequent collisions between reacting particles.
Q7
Medium
Which factor does NOT affect the rate of a chemical reaction?
A.
Temperature
B.
Surface area
C.
Color of the reactants
D.
Concentration
Show Answer & Explanation
Correct Answer: C
The color of the reactants does not influence the rate of a chemical reaction. Factors that do include temperature, surface area, and concentration, as they affect the frequency of particle collisions.
Q8
Hard
Which of the following statements regarding endothermic and exothermic reactions is incorrect?
A.
Endothermic reactions absorb heat from the surroundings.
B.
Exothermic reactions release energy in the form of heat.
C.
In an endothermic reaction, the enthalpy change is negative.
D.
Combustion of fuels is an example of an exothermic reaction.
Show Answer & Explanation
Correct Answer: C
In an endothermic reaction, the enthalpy change is positive, indicating that heat is absorbed, not released. Therefore, option C is incorrect, while the other options correctly describe the nature of endothermic and exothermic reactions.
Q9
Hard
What is the primary difference between exothermic and endothermic reactions in terms of energy change?
A.
Exothermic reactions absorb energy, while endothermic reactions release energy.
B.
Exothermic reactions release energy, while endothermic reactions absorb energy.
C.
Both exothermic and endothermic reactions release energy.
D.
Both reactions absorb energy from the surroundings.
Show Answer & Explanation
Correct Answer: B
Exothermic reactions release energy into the surroundings, causing an increase in temperature, while endothermic reactions absorb energy, leading to a decrease in temperature.
Q10
Hard
A student mixes 50 mL of 0.5 M hydrochloric acid with 50 mL of 0.5 M sodium hydroxide. What is the resulting pH of the solution?
A.
7
B.
1
C.
14
D.
3
Show Answer & Explanation
Correct Answer: A
When equal volumes of strong acid and strong base react, they neutralize each other. The resulting solution is neutral with a pH of 7.
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Chemical Reactions — IGCSE (Cambridge) IGCSE Chemistry Practice Questions Online
This page contains 145 practice MCQs for the chapter Chemical Reactions in IGCSE (Cambridge) IGCSE Chemistry. The questions are organized by difficulty — 44 easy, 76 medium, 25 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.