Chapter Exam

Chapter-6 Energetics of Reactions — Online MCQ Test

Q: When bonds are broken in a reaction, energy is:

Answer: B. Absorbed from the surroundings — Breaking bonds requires energy to be absorbed from surroundings, as energy was stored when those bonds formed.

Q: Consider the energy level diagram below: Reactants are at 100 kJ, the activation energy is 60 kJ, and products are at 85 kJ. What is the overall energy change, and what type of reaction is this?

Answer: B. -15 kJ, exothermic — Energy change = Products - Reactants = 85 - 100 = -15 kJ. Negative value indicates exothermic reaction.

Q: In an exothermic reaction, 150 kJ/mol is released. If this reaction is reversed (products converted back to reactants), the reverse reaction would be:

Answer: B. Endothermic, requiring 150 kJ/mol input — Reversing an exothermic reaction makes it endothermic with the same magnitude of energy change but opposite sign.

CHEMISTRY · Grade 10 · IGCSE cambridge

Practice Chapter-6 Energetics of Reactions with a free chapter-wise online MCQ test for IGCSE cambridge Grade 10 CHEMISTRY. This chapter covers: Exothermic and endothermic reactions energy level diagrams and bond making and breaking.. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter-6 Energetics of Reactions — Important Questions & Answers (FAQ)

Frequently asked questions from IGCSE cambridge Grade 10 CHEMISTRY — Chapter-6 Energetics of Reactions, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following best defines an exothermic reaction?

A. A reaction that absorbs heat energy from the surroundings
B. A reaction that releases heat energy to the surroundings ✓
C. A reaction that requires a catalyst to proceed
D. A reaction that increases the disorder of the system

Answer: B. A reaction that releases heat energy to the surroundings
An exothermic reaction releases heat energy to the surroundings, causing the temperature of the surroundings to increase.

What is the key difference between endothermic and exothermic reactions in terms of energy?

A. Endothermic reactions release energy; exothermic reactions absorb energy
B. Endothermic reactions absorb energy; exothermic reactions release energy ✓
C. Both reactions require the same amount of energy
D. Endothermic reactions are always faster than exothermic reactions

Answer: B. Endothermic reactions absorb energy; exothermic reactions release energy
Endothermic reactions absorb heat energy from surroundings, while exothermic reactions release heat energy to surroundings.

When bonds are broken in a reaction, energy is:

A. Released to the surroundings
B. Absorbed from the surroundings ✓
C. Converted to mass
D. Stored in the catalyst

Answer: B. Absorbed from the surroundings
Breaking bonds requires energy to be absorbed from surroundings, as energy was stored when those bonds formed.

Consider the energy level diagram below: Reactants are at 100 kJ, the activation energy is 60 kJ, and products are at 85 kJ. What is the overall energy change, and what type of reaction is this?

A. +15 kJ, endothermic
B. -15 kJ, exothermic ✓
C. +60 kJ, endothermic
D. -60 kJ, exothermic

Answer: B. -15 kJ, exothermic
Energy change = Products - Reactants = 85 - 100 = -15 kJ. Negative value indicates exothermic reaction.

In an exothermic reaction, 150 kJ/mol is released. If this reaction is reversed (products converted back to reactants), the reverse reaction would be:

A. Exothermic, requiring 150 kJ/mol input
B. Endothermic, requiring 150 kJ/mol input ✓
C. Exothermic, releasing 150 kJ/mol
D. Neutral, requiring no energy change

Answer: B. Endothermic, requiring 150 kJ/mol input
Reversing an exothermic reaction makes it endothermic with the same magnitude of energy change but opposite sign.

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