A-Level Chemistry Specification

Edexcel 9CH0

Section 12: Acid-base Equilibria

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#12.1

know that a Brønsted–Lowry acid is a proton donor and a Brønsted–Lowry base is a proton acceptor

Theory of acids and bases

#12.2

know that acid-base reactions involve the transfer of protons

Theory of acids and bases

#12.3

be able to identify Brønsted–Lowry conjugate acid-base pairs

Theory of acids and bases

#12.4

be able to define the term ‘pH’

pH

#12.5

be able to calculate pH from hydrogen ion concentration

pH

#12.6

be able to calculate the concentration of hydrogen ions, in mol dm-3, in a solution from its pH, using the expression [H+] = 10–pH

pH

#12.7

understand the difference between a strong acid and a weak acid in terms of degree of dissociation

Strong and weak acids

#12.8

be able to calculate the pH of a strong acid

Strong and weak acids

#12.9

be able to deduce the expression for the acid dissociation constant, Ka,for a weak acid and carry out relevant calculations

Strong and weak acids

#12.10

be able to calculate the pH of a weak acid making relevant assumptions

Strong and weak acids

#12.11

be able to define the ionic product of water, Kw

Ionic product of water

#12.12

be able to calculate the pH of a strong base from its concentration, using Kw

Strong and weak bases

#12.13

be able to define the terms ‘pKa’ and ‘pKw

Strong and weak acids Ionic product of water

#12.14

be able to analyse data from the following experiments:

i) measuring the pH of a variety of substances, e.g. equimolar solutions of strong and weak acids, strong and weak bases, and salts
ii) comparing the pH of a strong acid and a weak acid after dilution 10, 100 and 1000 times

Strong and weak acids

#12.15

be able to calculate Ka for a weak acid from experimental data given the pH of a solution containing a known mass of acid

Strong and weak acids

#12.16

be able to draw and interpret titration curves using all combinations of strong and weak monobasic acids and bases

pH titration curves

#12.17

be able to select a suitable indicator, using a titration curve and appropriate data

Acid-base indicators

#12.18

know what is meant by the term ‘buffer solution’

Buffer solutions

#12.19

understand the action of a buffer solution

Buffer solutions

#12.20

be able to calculate the pH of a buffer solution given appropriate data

Buffer solutions

#12.21

be able to calculate the concentrations of solutions required to prepare a buffer solution of a given pH

Buffer solutions

#12.22

understand how to use a weak acid–strong base titration curve to:

i) demonstrate buffer action
ii) determine Ka from the pH at the point where half the acid is neutralised

pH titration curves

#12.23

understand why there is a difference in enthalpy changes of neutralisation values for strong and weak acids

Strong and weak acids

#12.24

understand the roles of carbonic acid molecules and hydrogencarbonate ions in controlling the pH of blood

Buffer solutions

#12P9

CORE PRACTICAL 9: Finding the Ka value for a weak acid

pH titration curves