Name:
________________________
Class:
________________________
Date:
________________________
Chromatography
Time:
72 minutes
Marks:
68 marks
Comments:
Page 1 of 25
Q1.
The diagram shows a chromatogram for a food colouring.
(a)
How does the chromatogram show that the food colouring is a mixture?
___________________________________________________________________
___________________________________________________________________
(1)
(b)
A student makes measurements for spot C.
The table shows the results.
Distance in
mm
Distance moved by spot C
7
Distance moved by solvent
39
Calculate the Rf value for spot C.
Give your answer to 2 significant figures.
Use the results in the table.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Rf value = ____________________
(3)
Page 2 of 25
(c)
Plan a chromatography experiment to investigate the colours in an ink.
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___________________________________________________________________
___________________________________________________________________
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___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
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___________________________________________________________________
___________________________________________________________________
(6)
(Total 10 marks)
Page 3 of 25
Q2.
A student used paper chromatography to investigate the colours in different inks.
Figure 1 shows the apparatus the student used.
Figure 1
(a)
The student made two mistakes in setting up the apparatus.
Identify the two mistakes.
Describe the problem each mistake would cause.
Mistake 1 __________________________________________________________
Problem __________________________________________________________
___________________________________________________________________
___________________________________________________________________
Mistake 2 __________________________________________________________
Problem __________________________________________________________
___________________________________________________________________
___________________________________________________________________
(4)
Page 4 of 25
(b)
The student then set up the apparatus without making any mistakes.
Figure 2 shows his results.
Figure 2
What colours are in the black ink?
___________________________________________________________________
___________________________________________________________________
(1)
(c)
Which of the inks is the most soluble in the solvent?
Give a reason for your answer.
Ink
_____________________________________________________________
Reason ___________________________________________________________
___________________________________________________________________
(2)
Page 5 of 25
(d)
Use Figure 2 to complete the table below, then calculate the Rf value for red ink.
Distance in mm
Distance moved by red ink
________________________
Distance from start line to solvent front
________________________
The Rf value for red ink is calculated using the equation.
Rf =
Give your answer to two significant figures.
___________________________________________________________________
___________________________________________________________________
Rf value = _____________________________
(5)
(e)
How can you tell from Figure 2 that the Rf value for the blue ink is greater than the Rf
value for the red ink?
___________________________________________________________________
___________________________________________________________________
(1)
(Total 13 marks)
Page 6 of 25
Q3.
Race horses may be given drugs to improve their performance in races.
This is illegal in the UK.
After races, urine samples are collected from the horses.
These samples are tested for drugs.
Chromatography is one of the tests used to identify drugs in urine.
The diagram shows a chromatogram.
(a)
How do we know that sample 1 was a pure sample of caffeine?
___________________________________________________________________
___________________________________________________________________
(1)
Page 7 of 25
(b)
Calculate the Rf value for cocaine.
Give your answer to 2 significant figures.
Use information from the diagram.
Use the equation:
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Rf value of cocaine = ____________________
(4)
(c)
Give three conclusions about the urine sample from the horse.
Use information from the diagram.
1. _________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
___________________________________________________________________
3. _________________________________________________________________
___________________________________________________________________
(3)
(Total 8 marks)
Page 8 of 25
Q4.
Chromatography can be used to find out what substances a drug contains.
The diagram shows a chromatogram for seven different drugs.
(a)
Calculate the Rf value of drug G.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Rf value = ____________________
(4)
(b)
Describe what the diagram shows about drug D.
___________________________________________________________________
___________________________________________________________________
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___________________________________________________________________
(3)
Page 9 of 25
(c)
Which substance is most soluble in the solvent used in this chromatogram?
Give a reason for your answer.
___________________________________________________________________
___________________________________________________________________
(1)
(d)
Explain the result for drug F.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(Total 10 marks)
Page 10 of 25
Q5.
This question is about mixtures.
(a)
Which substance is a mixture?
Tick (✓) one box.
Air
Gold
Methane
Nitrogen
(1)
(b)
Food colourings are often mixtures of dyes.
What name is given to mixtures that are designed as useful products?
___________________________________________________________________
(1)
A student investigated a purple food colouring, Y, using chromatography.
The student compares Y with dyes A, B and C.
(c)
Figure 1 shows the apparatus used.
Figure 1
Page 11 of 25
Chromatography involves a stationary phase and a mobile phase.
Draw one line from each phase to what is used for that phase.
Use Figure 1.
Phase
What is used
Beaker
Mobile phase
Chromatography
paper
Food colouring
Stationary
phase
Pencil line
Solvent
(2)
Figure 2 shows the student’s results.
Figure 2
(d)
What three conclusions can you make about the dyes in food colouring Y?
1. _________________________________________________________________
___________________________________________________________________
2. _________________________________________________________________
___________________________________________________________________
3. _________________________________________________________________(3)
Page 12 of 25
(e)
In a different experiment a student recorded these results:
Distance moved by dye G = 60 mm
Distance moved by solvent = 80 mm
Calculate the Rf value of dye G.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Rf = _______________
(2)
(Total 9 marks)
Page 13 of 25
Q6.
A student used paper chromatography to identify the colours in a black ink.
The diagram below shows the student’s results.
(a)
What colours are in the black ink?
___________________________________________________________________
___________________________________________________________________
(2)
(b)
Suggest which colour is least soluble in the solvent.
Give a reason for your answer.
Colour
______________________
Reason
__________________________________________________________
___________________________________________________________________
(2)
Page 14 of 25
(c)
Use the diagram above to complete the table below.
Distance in mm
Distance moved by green
colour
Distance moved by solvent
Calculate the Rf value for the green colour.
Use the equation:
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Rf value = ________________________
(4)
(Total 8 marks)
Page 15 of 25
Q7.
(a)
This question is about gases.
Draw one line from each substance to the description of the substance.
(3)
Page 16 of 25
(b)
What is used to test for each of the gases?
Draw one line from each substance to the description of the substance.
(2)
(c)
Give two reasons why the percentage of carbon dioxide in the air has decreased in the
last 2.7 billion years.
Tick (✓) two boxes.
Combustion
Dissolved in oceans
Intense volcanic activity
Photosynthesis
Respiration
(2)
Page 17 of 25
Oxygen reacts with sulfur dioxide.
The reaction is reversible.
(d)
What is the symbol for a reversible reaction?
_________________________
(1)
(e)
Complete the sentence.
In a reversible reaction the forward reaction is exothermic, so the
reverse reaction is _________________________ .
(1)
(f)
A reversible reaction happens in apparatus which stops the escape of reactants and
products.
Complete the sentence.
Equilibrium is reached when the forward and reverse reactions happen at
exactly the same _________________________ .
(1)
(Total 10 marks)
Page 18 of 25
Mark schemes
Q1.
(a)
more than 1 dot in a vertical line
1
(b)
correct equation and substitution 7/39
accept Rf = distance moved by spot C / distance moved by
solvent
1
calculation and answer 0.1795
1
answer to 2 significant figures 0.18
1
(c)
Level 3: The plan would lead to the
production of a valid outcome. All key steps
are identified and logically sequenced.
5-6
Level 2: The plan would not necessarily lead
to a valid outcome. Most steps are identified,
but the plan is not fully logically sequenced.
3-4
Level 1: The plan would not lead to a valid
outcome. Some relevant steps are identified,
but links are not made clear.
1-2
No relevant content
0
Indicative content
•
put dots of known colours, and a dot of
the ink on a pencil line on the
chromatography paper.
•
place the bottom of the paper in water,
making sure the start line is above the
water
•
leave for solvent to rise up through
paper.
•
when solvent near top of paper, remove
and leave to dry.
•
compare positions of dots for known
colours with those from ink
6
[10]
Q2.
(a)
start line drawn in ink
1
Page 19 of 25
(so) line would run
1
start line below solvent level
1
(so) samples would wash off
1
(b)
red and blue
both colours needed
1
(c)
yellow
1
travels furthest up the paper
1
(d)
distance moved by red ink 13 ±1
measurements in cm max 1 mark for mps 1 and 2
1
distance from start line to solvent front 44 ±1
1
correct substitution
1
allow ecf from Table 4
correct answer
1
range if correct is 0.27 to 0.33
to 2 significant figures
1
(e)
moves further or nearer the top of the paper
1
[13]
Q3.
(a)
only one spot (on the chromatogram)
1
(b)
(distance moved by substance =) 4.2 (cm) and (distance moved by solvent =) 9.4
(cm)
allow in range 4.0–4.4 (for substance)
1
1
0.4468
1
0.45
Page 20 of 25
allow answer in range 0.43 to 0.47
1
(c)
(made of) three substances
1
two are unknown
1
one is cocaine
1
[8]
Q4.
(a)
1
5.1 ± 0.1 cm and 6.8 ± 0.1 cm
both measurements from figure
1
1
0.75
allow answer in range 0.72–0.77
allow ecf from incorrect measurements to final mark for 3
marks
an answer in range of 0.72–0.77 scores 4 marks
1
(b)
drug D contains one of the substances in E
1
drug D contains drug B
1
(and) a compound not found in any of the other drugs
allow an unknown substance
if no other marks awarded allow 1 mark for it is a mixture/
impure or it contains three substances
1
(c)
A as it has travelled the furthest in the solvent
ignore A unqualified
1
(d)
spot has stayed on the start line
1
(because) it is insoluble
1
[10]
Page 21 of 25
Q5.
(a)
air
1
(b)
formulation(s)
1
(c)
1
additional line from a box on the left negates the mark for that box
1
(d)
allow colour for dyes
Y contains 3 dyes
1
Y contains 2 known dyes
allow Y contains A and C
1
Y contains an unknown dye
allow Y does not contain dye B
1
alternative approach:
Y contains 3 dyes (1)
Y contains 1 known dye (1)
allow Y contains dye C
Y contains 2 unknown dyes (1)
allow Y does not contain dyes A and B
(e)
(Rf =)
1
Page 22 of 25
= 0.75
ignore units
1
[9]
Q6.
(a)
red and blue
1
unknown
1
both needed for the mark
(b)
red
ignore black
1
travels least far
dependent on correct colour allow closest to the
start line
1
(c)
distance moved by green colour = 12 mm
allow 10 to 14 mm
1
distance moved by solvent = 36 mm
allow 35 to 36 mm
1
allow correct substitution of student’s
measurements
1
Rf value = 0.33
allow correct answer from student’s
measurements for 2 marks
1
[8]
Q7.
Page 23 of 25
(a)
If more than one line is drawn from any one substance and
not crossed out, no mark is given for that substance. The
other marks can be awarded.
1
1
1
(b)
If more than one line is drawn from any one gas and not
crossed out, no mark is awarded for that gas.
The other mark can be awarded.
1
1
(c)
dissolved in oceans
1
photosynthesis
1
(d)
⇌
ignore any other words, formulae or symbols
Page 24 of 25
1
(e)
endothermic (reaction)
spelling must be correct
do not accept exothermic
1
(f)
rate (of reaction)
allow speed or velocity
do not accept any other response
1
[10]
Page 25 of 25