Exothermic and Endothermic Reactions

Exothermic and Endothermic Reactions MDCAT MCQs with answers

8 past paper MCQs on Exothermic and Endothermic Reactions, from the Thermochemistry and Energetics of Chemical Reactions unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.In an exothermic reaction, the heat content of the: (MDCAT 2024)

  1. reactants and products is equal
  2. reactants is more than that of the products
  3. products is more than that of the reactants
  4. reactants and products does not change
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Correct answer: (b) reactants is more than that of the products

Heat is given out, so the products hold less energy than the reactants and $\Delta H$ is negative.

2.Majority of reactions taking place at ordinary temperatures with -ΔH are (UHS MDCAT 2025)

  1. Endothermic
  2. Exothermic
  3. Thermally unstable
  4. Reversible
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Correct answer: (b) Exothermic

A negative enthalpy change means heat leaves the system, which is what exothermic means.

3.Select the exothermic reaction among the following: (NUMS MDCAT 2025)

  1. Thermal composition of P2O5
  2. Formation of atmospheric nitric oxide
  3. Burning of methane
  4. Sublimation of dry ice
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Correct answer: (c) Burning of methane

Burning methane gives out heat, so its enthalpy change is negative.

4.In endothermic reaction, the heat content of the (UHS MDCAT 2024)

  1. Reactants and products is equal
  2. Reactants is more than that of products
  3. Products is more than that of reactants
  4. Reactants & Products will not change
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Correct answer: (c) Products is more than that of reactants

An endothermic reaction takes heat in, so the products hold more energy than the reactants.

5.In the air, N2 and O2 occur naturally but they do not react to form oxides of nitrogen because: (PMC MDCAT 2022)

  1. Oxides of nitrogen are unstable
  2. Catalyst is required for the reaction
  3. The reaction is endothermic
  4. N2 and O2 do not react with each other
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Correct answer: (c) The reaction is endothermic

Nitrogen and oxygen combine only at the temperature of a spark or an engine, because the reaction absorbs heat.

6.Enthalpy change of combustion is exothermic because: (NUMS MDCAT 2022)

  1. Energy released in bond breaking is greater
  2. Energy released in bond making is greater
  3. Energy absorbed in bond breaking is greater
  4. Energy absorbed in bond making is greater
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Correct answer: (b) Energy released in bond making is greater

More energy comes out in forming the new bonds than goes in breaking the old ones.

7.Energy for the endothermic reaction is given a ____ value? (PMC Practice 2021)

  1. Positive
  2. Negative
  3. Zero
  4. Neither positive nor negative
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Correct answer: (a) Positive

An endothermic reaction takes heat in, so its enthalpy change is positive.

8.Reaction of water with quicklime results in the rise in the temperature of the system. Using the concept of an energy change, indicates the nature of the reaction? (UHS MDCAT 2018)

  1. Endothermic Reaction
  2. Non-Spontaneous Reaction
  3. Third Order Reaction
  4. Exothermic Reaction
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Correct answer: (d) Exothermic Reaction

Heat is given out, so the reaction is exothermic.

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