Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can explain the difference between Q, which describes a mixture at any moment, and K, the value Q reaches at equilibrium. (Guide: “Q at any moment, K at equilibrium”; Practice Q5)
- I can state that at equilibrium Qc = Kc and Qp = Kp, and that Q moves towards K as a reaction runs. (Guide: Figure 1; Practice Q5(d))
- I can explain that Kc uses concentrations and Kp uses partial pressures, so their values usually differ. (Guide: “Gases: Qp and Kp”; Practice Q5(b))
- I can explain why pure solids and pure liquids are left out of Q and K. (Guide: “What to leave out”; Practice Q7)
Skills
- I can write Kc for a reaction with gases, with each concentration raised to its coefficient. (Guide: Worked example 1; Practice Q1)
- I can write Kp for a heterogeneous reaction, leaving out the solids. (Guide: Worked example 3; Practice Q2, Q7)
- I can write Kc for a reaction in water, leaving out H₂O(l) but keeping H₂O(g) when it appears. (Practice Q1, Q3)
- I can substitute concentrations or partial pressures into Q and calculate its value. (Guide: Worked example 2; Practice Q4, Q5(c))
- I can plot Q against time with labelled axes and an even scale, and read K from the flat part. (Guide: Figure 1; Practice Q6)
Reasoning
- I can decide whether a mixture is at equilibrium by comparing Q with K. (Guide: Worked examples 2 and 3; Practice Q5(d))
- I can explain why two mixtures that start differently at the same temperature end with the same value of Q. (Practice Q6(e))
- I can explain why adding more of a solid does not change Q. (Guide: Worked example 3; Practice Q7(b))
All ticked? Move on to Topic 7.4, Calculating the Equilibrium Constant, or return to the course roadmap.