Suggested Activity 1: Titration of sodium
hydroxide with hydrochloric acid
Instructions and answers for teachers
and technicians
These instructions cover the learner activity section which can be found on page 13. This Practical
activity supports OCR GCSE Chemistry.
This is a suggested practical activity that can be used as part of teaching the GCSE (9-1)
Gateway Science (A) and Twenty First Century Science (B) specifications.
These are not controlled assessment tasks, and there is no
requirement to use these particular activities.
You may modify these activities to suit your learners and centre. Alternative activities are
available from, for example, Royal Society of Biology, Royal Society of Chemistry, Institute of
Physics, CLEAPSS and publishing companies, or of your own devising.
Further details are available in the specifications (Practical Skills Topics), and in these videos.
This resource is adapted from the Practical Chemistry project, developed
by the Nuffield Foundation and the Royal Society of Chemistry –
http://www.rsc.org/learn-chemistry/collections/experimentation/practical-
chemistry specifically the practical ‘Titrating sodium hydroxide with
hydrochloric acid’
http://www.rsc.org/learn-chemistry/resource/res00000697/titrating-
sodium-hydroxide-with-hydrochloric-acid.
Before carrying out any experiment or demonstration based on this guidance, it is the
responsibility of teachers to ensure that they have undertaken a risk assessment in
accordance with their employer’s requirements, making use of up-to-date information and
taking account of their own particular circumstances. Any local rules or restrictions issued
by the employer must always be followed.
CLEAPSS resources are useful for carrying out risk-assessments:
(http://science.cleapss.org.uk).
Centres should trial experiments in advance of giving them to learners. Centres may
choose to make adaptations to this practical activity, but should be aware that this may
affect the Apparatus and Techniques covered by the learner.
Introduction
In this activity, learners will practice their titration technique by titrating acid against alkali of known
concentration, then against a sample of alkali of unknown concentration.
It is suggested that prior technique practice with the glassware is carried out using distilled water
before titration with acids/alkalis are carried out.
Additionally, the suggested activity PAG7.1 The Vinegar Dilemma could be used to introduce the
ideas behind titration before tackling volumetric titration here.
DfE Apparatus and Techniques covered
The codes used below match the OCR Practical Activity Learner Record Sheet (Chemistry /
Combined Science) and Trackers (Chemistry / Combined Science) available online. There is no
requirement to use these resources.
By doing this experiment, learners have an opportunity to develop the following skills:
1 [1]: Use of appropriate apparatus to make and record a range of measurements accurately,
including: iv [vi]) volume of liquids
3 [8]: Use of appropriate apparatus and techniques for: ii) conducting and monitoring chemical
reactions, including appropriate reagents and/or techniques for the measurement of pH in different
situations
6 [11]: Safe use and careful handling of gases, liquids and solids, including: i) careful mixing of
reagents under controlled conditions; ii) using appropriate apparatus to explore chemical changes
and/or products
8: Use of appropriate qualitative reagents and techniques to analyse and identify unknown
samples or products including; iv) the determination of concentrations of strong acids and strong
alkalis
, Aims
To determine the concentration of a sample of sodium hydroxide
Intended class time
45-60 minutes
Links to Specifications:
Gateway Science (Suite A) – including Working Scientifically (WS)
C3.3e recognise that aqueous neutralisation reactions can be generalised to hydrogen ions
reacting with hydroxide ions to form water
C3.3h recall that relative acidity and alkalinity are measured by pH
C3.3i describe neutrality and relative acidity and alkalinity in terms of the effect of the
concentration of hydrogen ions on the numerical value of pH (whole numbers only)
C3.3j recall that as hydrogen ion concentration increases by a factor of ten the pH value of a
solution decreases by a factor of one
C3.3k describe techniques and apparatus used to measure pH
C5.1b describe the technique of titration
C5.1c explain the relationship between the volume of a solution of known concentration of a
substance and the volume or concentration of another substance that reacts completely together
CM5.1ii provide answers to an appropriate number of significant figures
CM5.1iii covert units where appropriate particularly from mass to moles
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