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LearnCambridge97012025–2027Paper 1 · Multiple ChoiceEquilibria

Paper 1 · Module

Equilibria

2 subtopics≈ 90 min in total

Start the module: Equilibrium and Kc Open graphing calculator

Equilibrium and Kc
At dynamic equilibrium in a closed system, forward and reverse rates are equal and concentrations are constant. Le Chatelier's principle: if conditions change, the equilibrium shifts to oppose the change. For $a\mathrm{A}+b\mathrm{B}\rightleftharpoons c\mathrm{C}+d\mathrm{D}$ , $K_c=\frac{[\mathrm{C}]^c[\mathrm{D}]^d}{[\mathrm{A}]^a[\mathrm{B}]^b}$ (products over reactants, powers = coefficients). Use an ICE table to find equilibrium concentrations. Only temperature changes $K_c$ : for exothermic forward reactions, raising $T$ lowers $K_c$ . Concentration and pressure changes shift the position but not $K_c$ ; catalysts change neither.
≈ 50 min
Brønsted–Lowry acids and bases
A Brønsted–Lowry acid is a proton (H⁺) donor; a base is a proton acceptor. Every acid–base reaction has two conjugate pairs: in $\mathrm{HCl+H_2O\rightarrow Cl^-+H_3O^+}$ , HCl/Cl⁻ and H₃O⁺/H₂O. Strong acids dissociate fully ( $\mathrm{HCl\rightarrow H^++Cl^-}$ ); weak acids partially ( $\mathrm{CH_3COOH\rightleftharpoons CH_3COO^-+H^+}$ ). $\mathrm{pH}=-\log_{10}[\mathrm{H^+}]$ ; for a strong monoprotic acid $[\mathrm{H^+}]=c$ . Water is amphoteric: it can act as an acid or a base.
≈ 40 min

Cambridge 9701 Equilibria — A Level Chemistry · Salam Academy