WJEC A Level Chemistry
WJEC A Level Chemistry 3.8 Equilibrium Constants Exam Questions
Free WJEC A Level Chemistry exam questions on 3.8 Equilibrium Constants, with mark schemes. Covers Kc, Kp, and the effect of conditions on equilibrium constants.
3.8 Equilibrium Constants 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.
StemUp mark scheme flashcards
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 3.8 Equilibrium Constants
This topic covers quantitative equilibrium.
What you need to know
- Kc Expression from concentrations at equilibrium, with units.
- Kp Expression using partial pressures and mole fractions.
- Temperature Only temperature changes the value of K.
- Calculations Finding equilibrium amounts from initial values.
Common mistakes in 3.8 Equilibrium Constants
- Saying pressure changes Kp.
- Including solids in Kc expressions for heterogeneous equilibria.
- Wrong units for K.
Try three 3.8 Equilibrium Constants exam-style questions
1. Write the Kc expression for H₂ + I₂ ⇌ 2HI. (1 mark)
Show the mark scheme answer
Kc = [HI]² / ([H₂][I₂]).
2. Explain the effect of increasing temperature on Kc for an exothermic reaction. (2 marks)
Show the mark scheme answer
Equilibrium shifts in the endothermic direction to the left (1), so Kc decreases (1).
3. Define mole fraction. (1 mark)
Show the mark scheme answer
Moles of a gas divided by the total moles of gas.
3.8 Equilibrium Constants FAQs
What does Equilibrium Constants cover?
Kc and Kp expressions, calculations and the effect of conditions.
Does a catalyst change K?
No, it only speeds up reaching equilibrium.
How are partial pressures found?
Partial pressure = mole fraction x total pressure.
Revise this topic with flashcards: WJEC A Level Chemistry Flashcards, with mark scheme answers for Anki and Quizlet.
