Cambridge International Paper
5 A Level Chemistry (9701)
Paper 5: Planning, Analysing
and Evaluation
1
,Contents INDEX Page number
-C1. Frequent Calculations and Other Details 3
-C2. Apparatus 5
-C3. Videos For Carrying Out Specific Uses of Apparatus 7
-C4. Graphs 8
-C5. Typical Past Paper Experiments with Diagrams and Explanations 14
-C6. Safety Considerations 19
-C7. Rinsing 19
-C8. Extra Useful Details from Past Papers 20
-C9. Explanation of Structure of the Exam and Marks 22
2
, AL
Frequent Calculations and Other Details
Rounding and Giving Values in Tables:
The general rule is that you shouldn't give your answer to a greater degree
of accuracy than the least accurate bit of data you are using. Unless, a
specific degree of accuracy is asked in the question.
So, if you are working with numbers like 25, 27.5 and 0.316, your least
accurate number is the 25 which is only quoted to 2 significant figures.
Your answer can't be any more accurate than that.
Frequent Calculations:
Simple Mole Calculations:
Revise mole calculations.
Calculations Involving Gases:
Here you may use that 1 mol equals 24dm3. You may also have to use the
ideal gas equation.
𝑃𝑉 = 𝑛𝑅𝑇
Pressure in Pa, volume in m3, number of moles of gas in mol, R constant of
the gas (8.31 J/mol K) and temperature in K.
Enthalpy Change Calculations:
In this case we must use this formula, 𝐸𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝐶ℎ𝑎𝑛𝑔𝑒 = 𝑚𝑐𝛥𝑇
3
,Rates of Reaction Calculations:
Calculating k from Initial Concentrations and Initial Rate:
Calculating k from Half-life:
For first order reactions, there is a formula to calculate k using the half-
life.
𝑘𝑡1 = 0.693
2
Where the symbol for half-life is 𝑡1 and it must be in seconds.
2
4
,Deducing Order of Reaction from Raw Data:
This can be done by plotting a graph to show how the concentration of a
particular reactant or product changes with time. Take tangents plat
various points along the curve which correspond to a particular
concentration of the reactant. Then calculate the gradient of each tangent
and this will be equal to the rate of the reaction. Finally, plot a graph of
rate of reaction against concentration.
Apparatus
Volumetric Flask:
A volumetric flask is used for making up fixed volumes of solutions of
accurately known concentrations. Volumetric flasks come in various sizes,
but the ones you are most likely to use in the lab at this level are 250 cm 3
and 100 cm3. To make accurate solutions you use this.
Pipettes:
Pipettes are used to measure out fixed volumes of liquids very accurately.
The most common sizes are 25 cm3 and 10 cm3.
5
,Burettes:
Burettes are used to measure out variable volumes of liquid very
accurately - including, of course, in titrations. The most common size is of
50 cm3. The most common use is to transfer a specific volume of a
substance to a volumetric flask. To transfer it we use the burette.
If you need to measure out some bigger volume of liquid, there is no
reason why you couldn't do this by refilling the burette. For example,
there was a CIE question which asked you how you would add exactly 100
cm3 of one solution to another one. The Examiner's Report suggested
using a burette, adding two separate lots of 50 cm3. But if you are going to
do this, be precise - say that you are going to use a 50 cm3 burette twice.
6
,Measuring Cylinders:
Measuring cylinders are not accurate enough if you need to add an exact
volume, and you won't get a mark if you suggest using one where a
burette or pipette would be more appropriate.
In titration work, a simple example of the use of a measuring cylinder is
where you need to add an excess of dilute sulphuric acid during a
potassium manganate(VII) titration. You might, for example, be told to
add 10 cm3 of dilute sulfuric acid to the liquid in the flask before you run in
the potassium manganate(VII) solution from the burette. A measuring
cylinder is fine for this, because all that matters is that the acid is in
excess. As long as that is true, the exact amount of acid added doesn't
matter.
Videos For Carrying Out Specific Uses of Apparatus
Making Accurate Solutions:
https://www.youtube.com/watch?v=g5azAxTywgc
Pipetting Technique:
https://www.youtube.com/watch?v=qorl6rKLmRs
Titration with Burette:
https://www.youtube.com/watch?v=9DkB82xLvNE
7
, Graphs
Use very sharp HB pencil, very good clean rubber and a good ruler.
Variables in Graphs:
Independent Variable:
Is the one which you are deciding to change. For example, you might be
measuring something at various different times, or at various different
temperatures, or at various different concentrations. Each of these would
be the independent variable. The independent variable always goes on the
x-axis.
Dependent Variable:
Is the one which changes because of the changes in the independent
variable. For example, the volume of a gas produced might be dependent
on how long the experiment is running for. The volume is dependent on
the time. The dependent variable always goes on the y-axis.
Scales:
Your graph should take up most of the graph paper, and not be squashed
up in one corner!
Plotting the Points:
The Examiner's Reports make a very strong recommendation that points
should be plotted using a small cross.
Drawing Best Fit Lines:
The data which you are given to plot is likely to have two separate
problems. The results that you are given to plot will all have some
"experimental error" added. That means that however accurately you plot
them, they probably won't all fall on a straight line or smooth curve.
It is quite likely that at least one of the results that you are given will be
anomalous. That means that the point is so far from the pattern shown by
the rest of the points that it must have been wrong.
8
,Straight Line:
Example:
When you have these results.
This is fairly obviously going to be a straight line, but before you do
anything else ask yourself if there are any points which don't seem to fit
tidily on that straight line - so-called "anomalous" points. In this case, the
third point falls underneath the trend for all the rest of the points. Before
you do anything else, check that you have plotted it correctly! Assuming
that they are plotted correctly, do not include any anomalous points when
you draw your line!
You are quite likely to be asked to account for any anomalous points you
find. In this case, the point is below the trend line. A smaller volume of
hydrogen was recorded than you would expect. What might cause that?
There are various possible reasons. You might have measured the volume
of the hydrogen wrongly, recording a smaller volume than you should
have. Or there might have been a leak of hydrogen from the apparatus
before you collected it. Alternatively, you might have mis-weighed the
magnesium. Perhaps you didn't have as much magnesium as you thought
you had.
The reasons will vary from experiment to experiment, but your answers
should be as precise as possible. You won't get any credit for saying
"There must have been an experimental error." You have to explain what
the error might have been, and why it made the point too high or too low.
9
, Drawing the Line:
The first thing to ask yourself each time is whether the line should go
through the origin (0,0).
Following the example above…
In this case, if you had zero mass of magnesium, you would obviously get
zero hydrogen produced - so the line must go through the origin. That is
really helpful! That gives you one point which is absolutely certain, with no
experimental error. That may well help you to decide exactly where to
place your line.
You are then going to draw a line of best fit which doesn’t necessarily
need to go through all of the points.
Draw your straight line with a ruler so that there is as even a scatter of
points either side of the line as you can manage (ignoring any anomalous
points).
Your final graph will look something like this:
10
5 A Level Chemistry (9701)
Paper 5: Planning, Analysing
and Evaluation
1
,Contents INDEX Page number
-C1. Frequent Calculations and Other Details 3
-C2. Apparatus 5
-C3. Videos For Carrying Out Specific Uses of Apparatus 7
-C4. Graphs 8
-C5. Typical Past Paper Experiments with Diagrams and Explanations 14
-C6. Safety Considerations 19
-C7. Rinsing 19
-C8. Extra Useful Details from Past Papers 20
-C9. Explanation of Structure of the Exam and Marks 22
2
, AL
Frequent Calculations and Other Details
Rounding and Giving Values in Tables:
The general rule is that you shouldn't give your answer to a greater degree
of accuracy than the least accurate bit of data you are using. Unless, a
specific degree of accuracy is asked in the question.
So, if you are working with numbers like 25, 27.5 and 0.316, your least
accurate number is the 25 which is only quoted to 2 significant figures.
Your answer can't be any more accurate than that.
Frequent Calculations:
Simple Mole Calculations:
Revise mole calculations.
Calculations Involving Gases:
Here you may use that 1 mol equals 24dm3. You may also have to use the
ideal gas equation.
𝑃𝑉 = 𝑛𝑅𝑇
Pressure in Pa, volume in m3, number of moles of gas in mol, R constant of
the gas (8.31 J/mol K) and temperature in K.
Enthalpy Change Calculations:
In this case we must use this formula, 𝐸𝑛𝑡ℎ𝑎𝑙𝑝𝑦 𝐶ℎ𝑎𝑛𝑔𝑒 = 𝑚𝑐𝛥𝑇
3
,Rates of Reaction Calculations:
Calculating k from Initial Concentrations and Initial Rate:
Calculating k from Half-life:
For first order reactions, there is a formula to calculate k using the half-
life.
𝑘𝑡1 = 0.693
2
Where the symbol for half-life is 𝑡1 and it must be in seconds.
2
4
,Deducing Order of Reaction from Raw Data:
This can be done by plotting a graph to show how the concentration of a
particular reactant or product changes with time. Take tangents plat
various points along the curve which correspond to a particular
concentration of the reactant. Then calculate the gradient of each tangent
and this will be equal to the rate of the reaction. Finally, plot a graph of
rate of reaction against concentration.
Apparatus
Volumetric Flask:
A volumetric flask is used for making up fixed volumes of solutions of
accurately known concentrations. Volumetric flasks come in various sizes,
but the ones you are most likely to use in the lab at this level are 250 cm 3
and 100 cm3. To make accurate solutions you use this.
Pipettes:
Pipettes are used to measure out fixed volumes of liquids very accurately.
The most common sizes are 25 cm3 and 10 cm3.
5
,Burettes:
Burettes are used to measure out variable volumes of liquid very
accurately - including, of course, in titrations. The most common size is of
50 cm3. The most common use is to transfer a specific volume of a
substance to a volumetric flask. To transfer it we use the burette.
If you need to measure out some bigger volume of liquid, there is no
reason why you couldn't do this by refilling the burette. For example,
there was a CIE question which asked you how you would add exactly 100
cm3 of one solution to another one. The Examiner's Report suggested
using a burette, adding two separate lots of 50 cm3. But if you are going to
do this, be precise - say that you are going to use a 50 cm3 burette twice.
6
,Measuring Cylinders:
Measuring cylinders are not accurate enough if you need to add an exact
volume, and you won't get a mark if you suggest using one where a
burette or pipette would be more appropriate.
In titration work, a simple example of the use of a measuring cylinder is
where you need to add an excess of dilute sulphuric acid during a
potassium manganate(VII) titration. You might, for example, be told to
add 10 cm3 of dilute sulfuric acid to the liquid in the flask before you run in
the potassium manganate(VII) solution from the burette. A measuring
cylinder is fine for this, because all that matters is that the acid is in
excess. As long as that is true, the exact amount of acid added doesn't
matter.
Videos For Carrying Out Specific Uses of Apparatus
Making Accurate Solutions:
https://www.youtube.com/watch?v=g5azAxTywgc
Pipetting Technique:
https://www.youtube.com/watch?v=qorl6rKLmRs
Titration with Burette:
https://www.youtube.com/watch?v=9DkB82xLvNE
7
, Graphs
Use very sharp HB pencil, very good clean rubber and a good ruler.
Variables in Graphs:
Independent Variable:
Is the one which you are deciding to change. For example, you might be
measuring something at various different times, or at various different
temperatures, or at various different concentrations. Each of these would
be the independent variable. The independent variable always goes on the
x-axis.
Dependent Variable:
Is the one which changes because of the changes in the independent
variable. For example, the volume of a gas produced might be dependent
on how long the experiment is running for. The volume is dependent on
the time. The dependent variable always goes on the y-axis.
Scales:
Your graph should take up most of the graph paper, and not be squashed
up in one corner!
Plotting the Points:
The Examiner's Reports make a very strong recommendation that points
should be plotted using a small cross.
Drawing Best Fit Lines:
The data which you are given to plot is likely to have two separate
problems. The results that you are given to plot will all have some
"experimental error" added. That means that however accurately you plot
them, they probably won't all fall on a straight line or smooth curve.
It is quite likely that at least one of the results that you are given will be
anomalous. That means that the point is so far from the pattern shown by
the rest of the points that it must have been wrong.
8
,Straight Line:
Example:
When you have these results.
This is fairly obviously going to be a straight line, but before you do
anything else ask yourself if there are any points which don't seem to fit
tidily on that straight line - so-called "anomalous" points. In this case, the
third point falls underneath the trend for all the rest of the points. Before
you do anything else, check that you have plotted it correctly! Assuming
that they are plotted correctly, do not include any anomalous points when
you draw your line!
You are quite likely to be asked to account for any anomalous points you
find. In this case, the point is below the trend line. A smaller volume of
hydrogen was recorded than you would expect. What might cause that?
There are various possible reasons. You might have measured the volume
of the hydrogen wrongly, recording a smaller volume than you should
have. Or there might have been a leak of hydrogen from the apparatus
before you collected it. Alternatively, you might have mis-weighed the
magnesium. Perhaps you didn't have as much magnesium as you thought
you had.
The reasons will vary from experiment to experiment, but your answers
should be as precise as possible. You won't get any credit for saying
"There must have been an experimental error." You have to explain what
the error might have been, and why it made the point too high or too low.
9
, Drawing the Line:
The first thing to ask yourself each time is whether the line should go
through the origin (0,0).
Following the example above…
In this case, if you had zero mass of magnesium, you would obviously get
zero hydrogen produced - so the line must go through the origin. That is
really helpful! That gives you one point which is absolutely certain, with no
experimental error. That may well help you to decide exactly where to
place your line.
You are then going to draw a line of best fit which doesn’t necessarily
need to go through all of the points.
Draw your straight line with a ruler so that there is as even a scatter of
points either side of the line as you can manage (ignoring any anomalous
points).
Your final graph will look something like this:
10
