OCR a Level Chemistry Studentbook 1

297 Pages·2015·17.771 MB·English

by  Dr Mike Smith

1
OCR
A LEVEL
CHEMISTRY
John Older
Mike Smith
9781471827068_OCR_A_Level_Chemistry.indb 1 30/03/15 2:42 PM
Acknowledgements
Photo credits
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© Andrew Lambert Photography/Science Photo Library, c © sciencephotos / Alamy, r © Andrew
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© John Older, Mike Smith 2015
First published in 2015 by
Hodder Education,
An Hachette UK Company
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Year 2019 2018 2017 2016 2015
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A catalogue record for this title is available from the British Library.
ISBN 9781471827068
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Contents
Get the most from this book iv
The questions in this book vi
Module 1 Development of practical skills in chemistry
Chapter 1 Practical skills 1
Module 2 Foundations in chemistry
Chapter 2 Atoms and electrons 10
Chapter 3 Compounds, formulae and equations 28
Chapter 4 Amount of substance – moles in solids and gases 39
Chapter 5 Amount of substance – moles in solution 62
Chapter 6 Types of reaction – precipitation, acid–base and redox 75
Chapter 7 Bonding and structure 89
Module 3 Periodic table and energy
Chapter 8 The periodic table and periodicity 115
Chapter 9 Group 2 and the halogens, qualitative analysis 127
Chapter 10 Enthalpy changes 143
Chapter 11 Rates and equilibria 165
Module 4 Core organic chemistry
Chapter 12 Basic concepts in organic chemistry 184
Chapter 13 Hydrocarbons 202
Chapter 14 Alcohols and haloalkanes 225
Chapter 15 Organic synthesis and analytical techniques (IR and MS) 244
Chapter 16 Maths in chemistry 266
Chapter 17 Preparing for the exam 275
Glossary 281
Index 284
Free online resources 288
The periodic table 290
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Get the most from this book
Welcome to the OCR A-level Chemistry 1 Student’s Book! This book
covers Year 1 of the OCR A-level Chemistry specification and all content
for the OCR AS Chemistry specification.
The following features have been included to help you get the most from
this book.
Prior knowledge
This is a short list of topics that
you should be familiar with before
starting a chapter. The questions
will help to test your understanding.
Key terms and formulae
These are highlighted in the text
and definitions are given in the
margin to help you pick out and
learn these important concepts.
Tips
These highlight important facts,
common misconceptions and
signpost you towards other
relevant chapters.
Test yourself questions
These short questions, found
throughout each chapter, are useful
for checking your understanding as
you progress.
iv
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G
e
Activities
t

t
These practical-based activities will h
help consolidate your learning and e

test your practical skills. m
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t

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Examples
Examples of questions or
calculations are included to illustrate
chapters and feature full workings
and answers.
Prac tice questions
You will find Practice questions, including multiple-choice
questions, at the end of every chapter. These follow the
style of the different types of questions with short and
longer answers that you might see in your examination, and
they are colour coded to highlight the level of difficulty.
Challenge questions are also provided.
Dedicated chapters for developing your Maths and Preparing for the exam
can be found at the back of this book.
v
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The questions in this book
The ‘Test yourself’ questions within the text of each chapter are
designed to check that you have understood the short section of
work that has just been covered. They are intended to be used
during the course but can also be helpful while you are revising.
The ‘Activities’ provide a chance to tackle a more extended
question and also provide a check that you are able to understand
and interpret experiments. The ‘Practice’ questions at the end of
the chapters cover a broader section of work. They include multiple
choice, structured and a smaller number of free response questions.
They also sometimes focus on the evaluation of some experimental
results. They are graded as follows:
Basic questions that everyone must be able to answer
without difficulty within the exam.
Questions which cover work that are a regular feature of
exams and that all competent candidates should be able to
handle.
More demanding questions that sometimes go beyond
the normal requirements of the exam but which the best
candidates should be able to do.
Challenge These are questions for the most able candidates to
test their full understanding and sometimes their ability
to use ideas in a novel situation.
It must be emphasised that although these questions cover the
skills and knowledge required to be successful in the examination,
they are not exam questions as such. Many only cover components
of questions which on the exam paper may come from more than
one section of the specification. When you are confident that your
knowledge base and your understanding is sufficient you must start
practising the past examination questions which are available from
the OCR website. Mark schemes are also available and these are
very helpful in making it clear what points examiners are looking
for and the depth that they expect. The best practice for the exam
is doing past exams.
vi
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Chapter 1
Practical skills
As part of the full A Level course you must carry out a number of
experiments which are separately assessed and lead to a practical
endorsement. Contained in the chapters of this book you will find
sections to help you understand the correct use of apparatus and the
methods required to carry out these tasks. However, within both the AS
and A Level courses, the written papers may also include questions that
require you to understand the limits of reliability of the techniques that
you have studied. This chapter gives some guidance to help support your
understanding of laboratory work.
The precision of apparatus
Each piece of laboratory apparatus used to measure a quantity has
a limit to its precision. For example, a basic balance may give a
measurement to the nearest gram; greater precision may be achieved
by using a balance capable of reading to one, two, three or even
four decimal places. The volume of a liquid can be measured using a
graduated beaker, a measuring cylinder or volumetric apparatus. Each of
these has a different level of precision. For most measuring equipment,
the manufacturer will give the maximum error that is inherent in using
that piece of apparatus; this is sometimes etched onto the apparatus
but, in other cases, will need to be looked up. Not all experiments
require the quantities measured to be exact, but if a quantitative result
is needed, you should be aware of the limitations of the apparatus used.
The maximum error is an inevitable part of using that piece of
equipment and is distinct from the competence with which the
experiment is carried out. Important decisions are sometimes based on
the results of experiments. For example, titrations are used in health
care, in the food industry and in forensic science. It is crucial that the
people making decisions based on the results obtained understand the
extent to which they can rely on the data from their analysis.
Measuring volumes of liquids
Beakers and conical fl asks
Markings on the sides of beakers and conical flasks serve only as a
very rough guide to the volume taken and it is impossible to assess the
maximum error involved in their use; however, it is likely to be large.
Calibrated beakers and conical flasks are not suitable for measuring
volumes reliably.
Measuring cylinders
Unless otherwise indicated, a useful rule of thumb for measuring
cylinders is that they have a maximum error of one-half of the
difference between the graduation marks. If a 25 cm3 measuring
cylinder has graduations every 0.5 cm3, the error is 0.25 cm3. If it is used
1
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to measure a volume of 20 cm3, then the true volume lies between
Tip
19.75 cm3 and 20.25 cm3. This can usefully be expressed as a percentage
In an exam you will be told the error because it can then be carried forward and applied to other results
maximum error that applies to a that are based on the measurement. In this case the percentage error is:
particular piece of apparatus.
0.25
× 100 = 1.25%
20.0
Key term A 100 cm3 measuring cylinder may have graduations every 1 cm3. The
maximum error is, therefore, 0.5 cm3. So, 20 cm3 measured in a 100 cm3
Percentage error is
cylinder is 20 ± 0.5 cm3. The percentage error is:
themaximumerror
× 100. 0.5
actualvalue × 100 = 2.5%
20.0
A 250 cm3 measuring cylinder usually has graduations every 2 cm3. The
maximum error is, therefore, 1 cm3. So, 20 cm3 measured in a 250 cm3
cylinder is 20 ± 1 cm3. This has a large percentage error of 5%.
The difference in the error made in taking these measurements is
considerable.
An increased error arises if both the start and end graduations are used to
measure a volume. For example, if 20 cm3 of water is measured by filling
a 100 cm3 measuring cylinder to the 100 cm3 mark and then pouring off
the water until the 80 cm3 mark is reached, both the start and the end
gradations are subject to a maximum error of 0.5 cm3. It is possible that
the starting volume could be 100.5 cm3 and the end volume 79.5 cm3.
The possible error is therefore 1 cm3 in the 20 cm3 measured, which is 5%
(although this is probably greater than the experimental reality).
When the pipette is filled, the
meniscus of the liquid should
sit on the volume mark on the Volumetric equipment
neck of the pipette. To do this
reliably requires practice. Volumetric apparatus includes pipettes, burettes and volumetric flasks.
● A pipette is usually selected when a small fixed volume of liquid or
solution is required.
● A burette is used to provide more variable volumes.
● A volumetric flask is used when a larger volume of liquid or solution
is required.
The solution in the pipette
should be allowed to run out
freely. When this is done a Using a pipette
small amount will remain in
the bottom of the pipette. A pipette is used to deliver a precise volume of solution (see Figure 1.1).
Touch the tip of the pipette The maximum error will vary according to the quality of its manufacture.
on the surface of the liquid
For routine work a 25.0 cm3 pipette with a maximum error of 0.06 cm3 is
that has been run out and
s then ignore any further often used.
kill solution that remains in
al s the pipette. The percentage error is:
ctic Figure 1.1 Using a pipette. 0.06 × 100 = 0.24%
a 25.0
r
P
1 Tip This is a much smaller error than would occur if a measuring cylinder had
r
e been used. The percentage error using a 25 cm3 measuring cylinder was
t
p Since the solution that is
a 1.25% (see above), hence the pipette is over 5 times more reliable.
Ch sucked into the pipette may be
Some pipettes are graduated to allow a volume less than the full
poisonous, a pipette filler must
capacity to be dispensed. These are useful but usually have a greater
always be used.
2 maximum error than a standard pipette.
9781471827068_OCR_A_Level_Chemistry.indb 2 30/03/15 2:42 PM
Using a burette T
h
When used correctly a volume measured by a burette has only a small error. e

p
Tip r
e
c
A funnel should be used to fill a burette so that solution is not spilled i
s
down the outside (Figure 1.2). Care must be taken not to overfill it. i
o
The tap should, of course, be closed during this procedure. However, n
before recording a volume, the funnel should be removed and some o
solution should be run out so that the space below the tap is filled. f

a
p
p
The required volume is measured as the difference between final and
a
initial readings. It is usual to read from the bottom of the meniscus but, r
a
because two readings are being subtracted, the top of the solution could
t
u
be used.
s
Burettes usually have graduations every 0.1 cm3 and should, therefore,
have a maximum error of 0.05 cm3. The volume delivered is the
difference between two measurements, so the volume obtained has a
potential uncertainty of 0.1 cm3. The percentage error will vary with the
volume that has been measured.
Test yourself
1 Figure 1.3 shows four burettes.
A B C D
12 22 9 2
13 23 10 3
Figure 1.2 A burette.
14 24 11 4
Tip
There are different grades of Figure 1.3
burette, so the maximum error in
any reading will vary. In an exam a) Record the readings for each of the four burettes.
the maximum error will be stated b) Calculate the percentage error in each of the burette readings. Assume
if you are required to consider it. the maximum error of each reading to be 0.05 cm3 and give your
answer to 2 decimal places.
c) If the burette reading in A is the initial reading and burette reading in
B is the final reading
i) calculate the titre volume
ii) calculate the percentage error in the titre volume.
Tip
If 250 cm3 were measured using Using a volumetric flask
a 50 cm3 burette filled five times, The mark on the neck of a volumetric flask indicates a specific volume.
the exercise would not only be The maximum error is almost certain to be etched on the flask and is
more tedious, but it would also usually of the order of 0.125%. If a volumetric flask is used to measure
have a greater error because 250.0 cm3, the volume obtained has a maximum error of:
each time the burette was used
0.125
there would be an error in the × 250 = 0.313 cm3
100
volume measured.
This means that the true volume lies between 249.7 cm3 and 250.3 cm3.
3
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