WJEC A Level Chemistry
WJEC A Level Chemistry 2.1 Thermochemistry Exam Questions
Free WJEC A Level Chemistry exam questions on 2.1 Thermochemistry, with mark schemes. Covers enthalpy changes, Hess's law, bond enthalpies and calorimetry.
2.1 Thermochemistry exam questions
1 question pack of real past exam questions with its mark scheme. Answer every question without notes, then mark your answers line by line against the mark scheme.
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WJEC A Level Chemistry Flashcards (Anki & Quizlet)
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Use them on Anki or Quizlet, then test yourself with the questions on this page.
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About WJEC A Level Chemistry 2.1 Thermochemistry
This topic covers energy changes in reactions. Expect Hess cycle and calorimetry calculations.
What you need to know
- Enthalpy changes Exothermic and endothermic reactions and standard conditions.
- Calorimetry q = mcΔT and calculating ΔH per mole.
- Hess's law Enthalpy change is independent of route; cycles using formation or combustion data.
- Bond enthalpies ΔH = bonds broken minus bonds formed, using average values.
Common mistakes in 2.1 Thermochemistry
- Using the mass of the solid instead of the solution in q = mcΔT.
- Getting the sign of ΔH wrong.
- Forgetting average bond enthalpies give approximate values.
Try three 2.1 Thermochemistry exam-style questions
1. Define standard enthalpy of formation. (2 marks)
Show the mark scheme answer
The enthalpy change when one mole of a compound is formed from its elements (1) in their standard states under standard conditions (1).
2. 50 cm³ of solution rises by 6.0 °C. Calculate q (c = 4.18 J g⁻¹ K⁻¹). (1 mark)
Show the mark scheme answer
q = 50 x 4.18 x 6.0 = 1254 J.
3. Explain why ΔH from bond enthalpies differs from the true value. (1 mark)
Show the mark scheme answer
Bond enthalpies are averages from many compounds.
2.1 Thermochemistry FAQs
What does Thermochemistry cover?
Enthalpy changes, calorimetry, Hess's law and bond enthalpies.
Which practical links here?
Determining an enthalpy change using calorimetry and Hess's law.
Why is ΔH negative for exothermic reactions?
The products have less energy than the reactants.
Revise this topic with flashcards: WJEC A Level Chemistry Flashcards, with mark scheme answers for Anki and Quizlet.
