AQA A LEVEL Topic 12 - ACIDS, BASES AND BUFFERS

• I can describe an acid as a proton donor, a base as a proton acceptor and acid–base equilibria as reactions involving the transfer of protons

• I can appreciate that the concentration of hydrogen ions in aqueous solution covers a very wide range, and therefore a logarithmic scale, the pH scale, is used as a measure of hydrogen ion concentration: pH = –log₁₀[H⁺]

• I can convert concentration of hydrogen ions into pH and vice versa

• I can calculate the pH of a solution of a strong acid from its concentration

• I understand that water is slightly dissociated, that K_W is derived from the equilibrium constant for this dissociation (K_W = [H⁺][OH^–]) and that the value of K_W varies with temperature

• I can use K_w to calculate the pH of a strong base from its concentration

• I can explain that weak acids and weak bases dissociate only slightly in aqueous solution, that K_a is the dissociation constant for a weak acid and that pK_a = –log₁₀K_a

• I can construct an expression for K_a and perform calculations relating the pH of a weak acid to the concentration of the acid and the dissociation constant, K_a

• I can convert K_a into pK_a and vice versa

• I can describe titrations of acids with bases and I can perform calculations for these titrations based on experimental results

• I can sketch and explain the shapes of typical pH curves in all combinations of weak and strong monoprotic acids and use pH curves to select an appropriate indicator

• I can carry out an experiment to investigate how pH changes when a weak acid reacts with a strong base and when a strong acid reacts with a weak base (Required Practical 9)

• I can describe a buffer solution as maintaining an approximately constant pH, despite dilution or addition of small amounts of acid or base, that acidic buffer solutions contain a weak acid and the salt of that weak acid and that basic buffer solutions contain a weak base and the salt of that weak base, and I can explain qualitatively the action of acidic and basic buffers

• I can calculate the pH of acidic buffer solutions

• I can describe applications of buffer solutions