MCQs — Energetics

Practice questions for Chemistry.

← Back to Energetics

Question 21

The energy released during an exothermic reaction, such as burning a fuel, can be practically used to:

A. Heat a room, drive an engine, or cook food

B. Absorb heat from the surroundings

C. Prevent any further chemical reactions from occurring

D. Only be used in laboratory settings

Question 22

Given C(s) + O2(g) -> CO2(g), with a standard enthalpy change of -393.5 kJ, this reaction is classified as:

A. Endothermic, since the enthalpy change is negative

B. Exothermic, since the enthalpy change is negative

C. Neither exothermic nor endothermic

D. Impossible to classify without more information

Question 23

Given 2H2(g) + O2(g) -> 2H2O(g), with a standard enthalpy change of -571.6 kJ, this reaction is classified as:

A. Exothermic, since the enthalpy change is negative

B. Endothermic, since the enthalpy change is negative

C. Neither exothermic nor endothermic

D. Impossible to classify without more information

Question 24

A chemical reaction that proceeds with the absorption of heat is called a(n):

A. Exothermic reaction

B. Endothermic reaction

C. Catalytic reaction

D. Spontaneous reaction

Question 25

In an endothermic reaction, heat is transferred:

A. From the system to the surroundings

B. From the surroundings to the system

C. Only within the system itself, with no exchange

D. Is destroyed entirely

Question 26

Given H2(g) + I2(g) -> 2HI(g), with a standard enthalpy change of +53.8 kJ, this reaction is classified as:

A. Exothermic, since the enthalpy change is positive

B. Endothermic, since the enthalpy change is positive

C. Neither exothermic nor endothermic

D. Impossible to classify without more information

Question 27

Given N2(g) + O2(g) -> 2NO(g), with a standard enthalpy change of +180.5 kJ, this reaction is classified as:

A. Exothermic, since the enthalpy change is positive

B. Endothermic, since the enthalpy change is positive

C. Neither exothermic nor endothermic

D. Impossible to classify without more information

Question 28

Since forming carbon monoxide (C + 1/2 O2 -> CO, DH = -110.5 kJ) releases less energy than forming carbon dioxide (C + O2 -> CO2, DH = -393.5 kJ), what can you conclude about these two reactions?

A. Both are endothermic, but CO2 formation absorbs more energy

B. Both are exothermic, but the formation of CO2 releases significantly more energy than the formation of CO

C. Only the formation of CO2 is exothermic

D. Neither reaction involves any energy change

Question 29

Why is the reaction of carbon with steam (C + H2O(g) -> CO(g) + H2(g), DH = +131.4 kJ) classified as endothermic?

A. Because its enthalpy change is positive, meaning the reaction absorbs heat from its surroundings

B. Because it produces a gas

C. Because carbon is a solid reactant

D. Because it involves water

Question 30

Energy in a chemical reaction can take many different forms. Besides heat, what other forms of energy are commonly involved in chemical changes?

A. Only heat is ever involved; no other forms exist

B. Light and work, among others

C. Only nuclear energy

D. Only kinetic energy of the whole system moving

Question 31

Exothermic and endothermic reactions are best distinguished from each other by:

A. Whether a solid or a gas is produced

B. Whether heat is evolved (released) or absorbed during the reaction

C. The number of atoms in the reactants

D. The color of the products

Question 32

The formation of nitrogen monoxide (N2 + O2 -> 2NO) requires an input of heat, and is therefore classified as a(n):

A. Exothermic reaction

B. Endothermic reaction

C. Non-thermochemical reaction

D. Catalyzed reaction only

Question 33

The amount of heat or thermal energy evolved or absorbed in a chemical reaction is called the:

A. Bond energy

B. Enthalpy of reaction

C. Activation energy

D. Kinetic energy

Question 34

The sign of the enthalpy of reaction is negative for:

A. Endothermic reactions

B. Exothermic reactions

C. Reactions with no energy change

D. All chemical reactions, without exception

Question 35

The sign of the enthalpy of reaction is positive for:

A. Exothermic reactions

B. Endothermic reactions

C. Reactions with no energy change

D. All chemical reactions, without exception

Question 36

Enthalpy of reaction measured at 25 degrees Celsius (298K) and one atmospheric pressure is known as the:

A. Bond dissociation energy

B. Standard enthalpy change

C. Activation energy

D. Free energy

Question 37

The standard enthalpy change of a reaction is conventionally denoted by the symbol:

A. DE

B. DH degree

C. DG

D. DS

Question 38

Why is a 'standard' set of conditions (25 degrees C and 1 atmosphere) specified when reporting enthalpy of reaction values?

A. Because enthalpy values never actually change with conditions

B. Because enthalpy values can vary with temperature and pressure, so a standard reference condition allows fair comparison between reactions

C. Because standard conditions are simply a legal requirement with no scientific basis

D. Because reactions cannot occur under any other conditions

Question 39

If a reaction's standard enthalpy change is reported as negative, what does this tell you about the reaction?

A. That the reaction absorbs heat from its surroundings

B. That the reaction is exothermic, releasing heat to its surroundings

C. That the reaction cannot actually occur

D. That the reaction produces no products

Question 40

If a reaction's standard enthalpy change is reported as positive, what does this tell you about the reaction?

A. That the reaction is exothermic

B. That the reaction is endothermic, absorbing heat from its surroundings

C. That the reaction produces no products

D. That the reaction is instantaneous

🎯 How to get the most out of these questions

Attempt each question before revealing the answer.
Read the explanation even when you answered correctly — it reinforces the concept.
Note down any question you got wrong and revisit it the next day.
Use the pagination below the list to work through every page — do not stop at page 1.

📌 MCQs — FAQs

Are answers included for every question in this section?

Yes — each published question includes an answer. Explanations are shown where they have been added.

Can I print these questions?

Yes — use your browser's print option (Ctrl+P / Cmd+P) to print or save the page as PDF.

How often are questions updated?

New questions are added regularly. If a paper pattern changes, existing questions are reviewed and updated.