Edexcel A-level Chemistry Student Guide: Practical Chemistry

240 Pages·2017·2.115 MB·English

by  David Scott

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© David Scott 2017
ISBN 978-1-4718-8567-9
eISBN 978-1-4718-8569-3
First printed 2017
Impression number 5 4 3 2 1
Year 2020 2019 2018 2017
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This guide has been written specifically to support students preparing for
the Edexcel AS and A-level Chemistry examinations. The content has been
neither approved nor endorsed by Edexcel and remains the sole
responsibility of the author.
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Contents
About this book
Core Practicals
1 Measure the molar volume of a gas
2 Use a standard solution to find the concentration of a
solution of sodium hydroxide
3 Find the concentration of a solution of hydrochloric acid
4 Investigation of the rates of hydrolysis of halogenoalkanes
5 Investigation of the oxidation of ethanol
6 Chlorination of 2-methylpropan-2-ol using concentrated
hydrochloric acid
7 Analysis of some inorganic and organic unknowns
8 To determine the enthalpy change of a reaction using Hess’s
law
9 Finding the K value for a weak acid
a
10 Investigating some electrochemical cells
11 Redox titration
12 The preparation of a transition metal complex
13a Following the rate of the iodine–propanone reaction by a
titrimetric method
13b Investigating a ‘clock reaction’ to determine a rate equation
14 Finding the activation energy of a reaction
15 Analysis of some inorganic and organic unknowns
16 The preparation of aspirin
Questions & Answers
Practical exam-style questions
Glossary
Index
About this book
The purpose of this guide is to help you to prepare for practical-based
questions that you will encounter in papers 1 and 2 of the Edexcel AS
Chemistry qualification and papers 1, 2 and 3 in the full Edexcel A-level
Chemistry qualification.
All papers in the A-level examination will examine ‘Working as a chemist’.
This means students:
• working scientifically, developing competence in manipulating quantities
and their units, including making estimates
• experiencing a wide variety of practical work, developing practical and
investigative skills by planning, carrying out and evaluating experiments,
and becoming knowledgeable about the ways in which scientific ideas are
used
• developing the ability to communicate their knowledge and
understanding of chemistry
• acquiring these skills through examples and applications from the entire
course
In particular, paper 3 covers the general and practical principles of
chemistry. It is of 2 hours and 30 minutes duration and is worth 120 marks.
This paper may draw on any of the topics in this specification and includes:
• synoptic questions that may draw on two or more different topics
• questions that assess conceptual and theoretical understanding of
experimental methods (indirect practical skills), which will draw on
students’ experiences of the core practicals
In the AS examination there are just two papers and questions based on
practical work may be set in both papers.
During your AS/Year 1 chemistry course you will tackle eight core practical
investigations and a further eight practical investigations if you are
preparing for the full A-level qualification. You will need to keep a record
of your observations and inferences as you progress, and take time to reflect
on how the procedures help to illustrate the theoretical ideas you study. If
you simply follow practical instructions uncritically, questions on all three
papers that require you to have a full appreciation of practical chemistry
will catch you out. If, however, you think carefully about why you are
carrying out certain procedures and are aware of their possible limitations,
you will be in a better position to answer these questions and gain full
credit.
This guide has two sections:
• The first section takes you through the eight AS/Year 1 core practical and
the eight A-level/Year 2 core practical investigations, as detailed in the
Edexcel (8CH0/9CH0) specification. Each practical is considered in
context and links are made to the theoretical aspects of the course. The
questions posed in each core practical will test your full understanding of
the procedure and how improvements might be made. Throughout, issues
relating to precision, uncertainty and handling of data appropriately are
considered as they are encountered.
• The Questions & Answers section consists of exam-style questions of the
type you can expect to encounter in papers 1 and 2 at AS, and in papers 1,
2 and 3 at A-level. Each question includes commentary on how the
question should be tackled and how marks are awarded, and is
accompanied with a sample answer.
Specification details and supplementary information can be found at
http://qualifications.pearson.com/en/qualifications/edexcel-a-
levels/chemistry-2015.html
Core Practicals
Core practical 1
Measure the molar volume of a gas
In this practical, known quantities of reactants are combined to produce a
gas, which is collected over water. By knowing the relationship between the
number of moles of reactants and products as shown in the balanced
equation, it is possible to estimate a value for the volume of 1 mole of a gas.
Make sure that you are comfortable converting masses of solids into moles
and volumes of gases into moles.
For solids (and liquids):
For gases:
The procedure
1 Place 30 cm3 of 1 mol dm−3 ethanoic acid in a boiling tube.
2 Set up the apparatus as shown in Figure 1.
3 Place approximately 0.05 g of calcium carbonate in a test tube and weigh
the test tube and its contents accurately.
4 Removing the bung from the boiling tube, add the contents of the test tube
and quickly replace the bung.
5 As the reaction progresses, the gas is collected over water.
6 Once the reaction is complete, measure the volume of gas collected in the
measuring cylinder.
7 Reweigh the test tube that contained the calcium carbonate.
8 Repeat the experiment six more times, increasing the mass of the calcium
carbonate by about 0.05 g each time, up to a maximum of 0.40 g.
The reaction is represented in the following equation: