Lesson 3.1.4.1

3.1.4.1 Enthalpy change Quiz: AQA Chemistry, Unit 1

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.4.1, Enthalpy change: 20 multiple choice questions for the AQA Chemistry (7405), Unit 1: Physical chemistry, written with Revision Ninja.

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The 20 questions

  1. What is an exothermic reaction?

    • A reaction that takes in energy from the surroundings, so the enthalpy change is positive
    • A reaction that releases energy to the surroundings, so delta H is negative
    • A reaction involving no energy change, so the temperature of the surroundings stays fixed
    • A reaction with delta H equal to zero, so no net heat flows in or out of the system

  2. Enthalpy change, delta H, is the heat energy change measured under which conditions?

    • Constant temperature only
    • Constant mass
    • Constant volume
    • Constant pressure

  3. What are the standard conditions referred to in the specification?

    • 1000 kPa and 25 C, a high-pressure setting
    • 100 kPa and a stated temperature
    • 50 kPa and 273 K, a reduced-pressure setting
    • 1 atm and 0 C, as used for gas tables

  4. What is the definition of standard enthalpy of combustion?

    • The energy needed to break one mole of bonds in a substance in the gas phase under standard conditions
    • The enthalpy change when one mole of a substance dissolves in water to form a dilute solution
    • The enthalpy change when one mole of a compound forms from its elements in their standard states
    • The enthalpy change when one mole of a substance burns completely in oxygen under standard conditions

  5. What is the definition of standard enthalpy of formation?

    • The energy needed to break one mole of bonds in a gaseous molecule under standard conditions, averaged
    • The enthalpy change when one mole of a substance burns completely in excess oxygen under standard conditions
    • The enthalpy change when one mole of ions is dissolved in water to form a solution at standard conditions
    • The enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions

  6. Which reaction is endothermic?

    • Burning magnesium ribbon in air to form magnesium oxide, which gives off heat
    • Dissolving ammonium nitrate in water, which makes the solution cold
    • Neutralising hydrochloric acid with sodium hydroxide, which warms the mixture
    • Combustion of methane in excess oxygen, which releases a large amount of heat

  7. What is the sign of delta H for an endothermic reaction?

    • Positive
    • Zero
    • Equal to the relative molecular mass
    • Negative

  8. Which equation represents the standard enthalpy of formation of carbon dioxide?

    • CO2(g) -> C(s) + O2(g)
    • C(g) + 2O(g) -> CO2(g)
    • 2C(s) + O2(g) -> 2CO(g)
    • C(s) + O2(g) -> CO2(g)

  9. Which equation represents the standard enthalpy of combustion of methane?

    • CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l)
    • CH4(g) -> C(s) + 2H2(g)
    • CH4(g) + O2(g) -> CO2(g) + H2O(g)
    • C(s) + 2H2(g) -> CH4(g)

  10. Which equation represents the standard enthalpy of formation of water?

    • H(g) + O(g) -> H2O(l)
    • 2H2(g) + O2(g) -> 2H2O(l)
    • H2(g) + 1/2 O2(g) -> H2O(l)
    • H2O(l) -> H2(g) + 1/2 O2(g)

  11. A 50.0 g sample of water rises in temperature by 5.0 K. Using c = 4.18 J g-1 K-1, what is the heat change, q?

    • 10450 J
    • 2090 J
    • 209 J
    • 1045 J

  12. Dissolving 1.00 g of NaOH (Mr = 40) in 100 g of water raises the temperature by 5.0 K. Using c = 4.18 J g-1 K-1, what is the enthalpy change per mole of NaOH?

    • +83.6 kJ mol-1
    • -83.6 kJ mol-1
    • -209 kJ mol-1
    • -2.09 kJ mol-1

  13. Which equation represents the standard enthalpy of combustion of ethanol?

    • 2C2H5OH(l) + 3O2(g) -> 4CO2(g) + 3H2O(l)
    • C2H5OH(l) + O2(g) -> CO2(g) + H2O(l)
    • C2H5OH(l) + 3O2(g) -> 2CO2(g) + 3H2O(l)
    • C2H5OH(l) + 2O2(g) -> 2CO2(g) + 3H2O(l)

  14. The standard enthalpy of formation of liquid water is -286 kJ mol-1. What is the enthalpy change for H2O(l) -> H2(g) + 1/2 O2(g)?

    • -286 kJ mol-1
    • +286 kJ mol-1
    • -572 kJ mol-1
    • +143 kJ mol-1

  15. A reaction releases 50 kJ of heat when 0.10 mol of reactant is used. What is the enthalpy change per mole?

    • -50 kJ mol-1
    • +500 kJ mol-1
    • -5 kJ mol-1
    • -500 kJ mol-1

  16. Why is the enthalpy of the products higher than the reactants in an endothermic reaction?

    • The products have less enthalpy, so delta H is positive
    • The reactants have higher enthalpy, so the surroundings gain energy
    • The products have more enthalpy than the reactants, so delta H is positive
    • Delta H is always negative for reactions in solution

  17. Burning 0.44 g of propane (Mr = 44) releases 22.2 kJ of heat. What is the enthalpy of combustion per mole?

    • -222 kJ mol-1
    • -2220 kJ mol-1
    • -44.4 kJ mol-1
    • -22.2 kJ mol-1

  18. Which species has a standard enthalpy of formation of zero?

    • O3(g)
    • H(g)
    • O2(g)
    • O(g)

  19. Which expression gives the heat change, q, used in calorimetry?

    • q = delta T / mc
    • q = m / c delta T
    • q = c / m delta T
    • q = mc delta T

  20. What does delta H298 mean?

    • Enthalpy change measured at 298 K and a pressure of 100 kPa
    • Enthalpy change measured at 273 K and 1 atm
    • Enthalpy change measured at 298 K and constant volume
    • Enthalpy change at 100 K and 298 kPa

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