MCQs — Energetics

Practice questions for Chemistry.

← Back to Energetics

Question 41

The enthalpy of reaction is essentially a way of quantifying:

A. How fast a reaction proceeds

B. How much heat energy is evolved or absorbed during a chemical reaction

C. The color change during a reaction

D. The number of moles of catalyst used

Question 42

A reaction has a standard enthalpy change of -393.5 kJ. Based on the sign convention, this reaction is:

A. Endothermic

B. Exothermic

C. Neither exothermic nor endothermic

D. Impossible to classify

Question 43

A reaction has a standard enthalpy change of +53.8 kJ. Based on the sign convention, this reaction is:

A. Exothermic

B. Endothermic

C. Neither exothermic nor endothermic

D. Impossible to classify

Question 44

Does the enthalpy of reaction tell you how fast a reaction proceeds, or how much heat it evolves/absorbs?

A. It tells you how fast the reaction proceeds only

B. It tells you how much heat is evolved or absorbed, not how fast the reaction proceeds

C. It tells you both equally

D. It tells you neither; enthalpy is unrelated to heat

Question 45

The amount of energy required to break one mole of a particular bond to form neutral atoms is called the:

A. Bond energy

B. Bond dissociation energy

C. Activation energy

D. Enthalpy of formation

Question 46

The amount of energy released when neutral atoms form one mole of a particular bond is called the:

A. Bond dissociation energy

B. Bond energy

C. Activation energy

D. Lattice energy

Question 47

The enthalpy change in a chemical reaction is essentially the sum of the energies:

A. Absorbed in bond breaking and released in bond forming

B. Only absorbed during the reaction, with no release considered

C. Only released during the reaction, with no absorption considered

D. Required to heat the reaction vessel

Question 48

What determines whether an overall reaction absorbs or releases energy, based on bond energies and bond dissociation energies?

A. Only the number of atoms in the reactants

B. The difference between the bond dissociation energy (needed to break bonds) and the bond energy (released in forming bonds)

C. The physical state of the reactants only

D. The color of the reactants

Question 49

The general formula for calculating a reaction's standard enthalpy change from bond energy data is:

A. Standard enthalpy change = sum of bond energies of reactants - sum of bond dissociation energies of products

B. Standard enthalpy change = sum of bond dissociation energies of reactants - sum of bond energies of products

C. Standard enthalpy change = sum of bond energies of reactants + sum of bond energies of products

D. Standard enthalpy change is unrelated to bond energy data

Question 50

If the sum of bond dissociation energies of the reactants is greater than the sum of bond energies of the products, the overall reaction will be:

A. Exothermic, since less energy is required to break bonds than is released

B. Endothermic, since more energy is required to break the reactant bonds than is released in forming the product bonds

C. Impossible to determine from this information

D. Unaffected by bond energies

Question 51

In the worked calculation for hydrogen and iodine forming hydrogen iodide, the first step of the problem-solving strategy is to:

A. Substitute bond energy values immediately

B. Write the balanced chemical equation

C. Measure the reaction's temperature

D. Look up the melting point of the product

Question 52

The second step in this problem-solving strategy is to:

A. Show all the reactants and products in the gaseous state

B. Convert all quantities into moles per litre

C. Calculate the reaction's rate

D. Determine the reaction's catalyst

Question 53

The third step in this problem-solving strategy is to:

A. Substitute the relevant bond energy values into the enthalpy formula and solve

B. Repeat the experiment multiple times

C. Measure the reaction's activation energy directly

D. Ignore the bond energy values entirely

Question 54

Given that the bond energies of H-H, I-I, and H-I are 436 kJ/mol, 151 kJ/mol, and 299 kJ/mol respectively, the sum of the bond dissociation energies of the reactants (H2 and I2) is:

A. 436 kJ/mol

B. 587 kJ/mol

C. 299 kJ/mol

D. 598 kJ/mol

Question 55

Continuing the same calculation, the sum of bond energies of the products (2 moles of HI) is:

A. 299 kJ/mol

B. 587 kJ/mol

C. 598 kJ/mol

D. 151 kJ/mol

Question 56

Using these values, the standard enthalpy change for H2(g) + I2(g) -> 2HI(g) is calculated to be approximately:

A. +11 kJ/mol

B. -11 kJ/mol

C. +587 kJ/mol

D. -598 kJ/mol

Question 57

Based on this calculated value (-11 kJ/mol), is the formation of hydrogen iodide from hydrogen and iodine exothermic or endothermic?

A. Endothermic, since the calculated enthalpy change is negative

B. Exothermic, since the calculated enthalpy change is negative

C. Neither, since the value is too small to matter

D. Impossible to determine from this value

Question 58

It is noted that enthalpy values calculated using bond energy data are often:

A. Identical to values determined experimentally, with no exceptions

B. Different from values determined experimentally

C. Impossible to calculate at all

D. Only valid for gases, never for liquids or solids

Question 59

Why might a calculated enthalpy value (using average bond energy data) differ from an experimentally measured value?

A. Because bond energies used in calculations are typically average values across many different compounds, whereas the actual bonds in a specific molecule may have slightly different real energies

B. Because calculations are always more accurate than experiments

C. Because experimental measurements never actually involve any energy

D. Because bond energy data is entirely fictional

Question 60

Given that the bond energies of H-H, F-F, and H-F are 436 kJ/mol, 155 kJ/mol, and 567 kJ/mol respectively, the sum of the bond dissociation energies of the reactants (H2 and F2) is:

A. 436 kJ/mol

B. 155 kJ/mol

C. 591 kJ/mol

D. 567 kJ/mol

🎯 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.