5.1.3 Acids, Bases and Buffers

Question 1

describe an acid as a species that can

donate a proton and a base as a species that

can accept a proton

Question 2

illustrate, using ionic equations, the role of H+

in the reactions of acids with metals,

carbonates, bases and alkalis

Question 3

describe and use the term conjugate acid–

base pairs;

Question 4

explain qualitatively, in terms of dissociation,

the differences between strong and weak

acids;

Question 5

explain that the acid dissociation constant,

Ka, shows the extent of acid dissociation;

Question 6

deduce, for weak acids, expressions for Ka

and pKa;

Question 7

define pH as pH = –log[H+]; [H+] = 10–pH;

Question 8

state and use the expression for the ionic

product of water, Kw;

Question 9

calculate pH from [H+(aq)] and [H+(aq)] from

pH for:

(i) strong monobasic acids,
(ii) weak monobasic acids,
(iii) strong bases, using Kw;

Question 10

calculate Ka for a weak acid, given

appropriate data;

Question 11

describe a buffer solution as a system that

minimises pH changes on addition of small

amounts of an acid or a base

Question 12

state that a buffer solution can be made from

a weak acid and a salt of the weak acid, eg

CH3COOH/CH3COONa;

Question 13

explain the role of the conjugate acid–base

pair in an acid buffer solution, eg

CH3COOH/CH3COO–, in the control of pH;

Question 14

calculate the pH of a buffer solution, from the

Ka value of a weak acid and the equilibrium

concentrations of the conjugate acid–base

pair;

Question 15

explain the role of carbonic acid–

hydrogencarbonate as a buffer in the control

of blood pH

Question 16

for acid–base titration pH curves for strong

and weak acids and bases:

(i) interpret, or sketch, their shapes,
(ii) explain the choice of suitable indicators

for acid–base titrations, given the pH

range of the indicator;

Question 17

define and use the term enthalpy change of

neutralisation and calculate enthalpy

changes from appropriate experimental

results