Chemistry 9701/53 October/November 2025: question paper and mark scheme
Cambridge AS & A Level Chemistry (9701), Paper 5 Planning, Analysis and Evaluation, October/November 2025. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
The concentration of aqueous chloride ions can be found by titration with aqueous silver nitrate,
AgNO3(aq).
Ag+(aq) + Cl –(aq) AgCl(s)
The indicator used is aqueous potassium chromate(VI), K2CrO4(aq).
As AgNO3(aq) is added to aqueous chloride ions, a white precipitate of AgCl(s) is formed.
When all the chloride ions have reacted, further addition of AgNO3(aq) leads to the formation of a red precipitate of silver chromate(VI), Ag2CrO4(s). The first appearance of the red precipitate
shows the end-point of the titration.
A student carries out an experiment to determine the number of molecules of water of crystallisation, x, in hydrated barium chloride, BaCl 2•xH2O(s).
(a) The student makes 250.0 cm3 of 0.0500 mol dm–3 AgNO3(aq) to use for the titration.
(i) Calculate the mass of solid silver nitrate, AgNO3(s), needed to make 250.0 cm3 of
0.0500 mol dm–3 AgNO3(aq).
Give your answer to two decimal places.
mass of AgNO3(s) = …… g [1]
(ii) Describe how the student should make 250.0 cm3 of 0.0500 mol dm–3 AgNO3(aq) starting from the mass of AgNO3(s) calculated in (a)(i) in a 50 cm3 beaker.
Give the name and size of any key apparatus used.
Write your answer using a series of numbered steps.
…… [3]
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(b) The student uses the following method.
step 1 Dissolve 1.58 g of BaCl 2•xH2O(s) to form 250 cm3 of aqueous solution. Label this solution A.
step 2 Transfer 20.0 cm3 of solution A into a conical flask.
step 3 Add aqueous sodium sulfate, Na2SO4(aq), to the flask and swirl the mixture to remove barium ions from the solution.
step 4 Add 2–3 drops of K2CrO4(aq) indicator to the flask.
step 5 Titrate the contents of the flask against 0.0500 mol dm–3 AgNO3(aq).
step 6 Repeat steps 2 to 5 to collect sufficient data for analysis.
(i) Suggest a suitable piece of apparatus for transferring 20.0 cm3 of solution A in step 2.
…… [1]
(ii) Suggest why barium ions are removed in step 3 before performing the titration.
…… [1]
(iii) Suggest why chemically resistant gloves should be worn to carry out step 4.
…… [1]
(c) The student’s results are shown in Table 1.1.
Table 1.1
rough titration titration 1 titration 2 titration 3
burette reading
20.10 40.55 20.75 20.90
(final) / cm3 burette reading
0.00 20.25 0.05 0.30
(initial) / cm3 titre / cm3 20.10 20.30 20.70 20.60
The student uses the titres from titrations 2 and 3 shown in Table 1.1 to calculate a mean titre value of 20.65 cm3.
(i) Explain why only these two values are used.
…… [1]
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(ii) Calculate the percentage error in the titre volume for titration 3.
Show your working.
percentage error = …… [1]
(d) The equation for the reaction of silver nitrate with barium chloride is shown.
2AgNO3(aq) + BaCl 2(aq) Ba(NO3)2(aq) + 2AgCl(s)
(i) Calculate the amount, in mol, of AgNO3(aq) in the mean titre of 20.65 cm3.
amount of AgNO3 = …… mol [1]
(ii) Calculate the amount, in mol, of BaCl 2(aq) in 250 cm3 of solution A.
amount of BaCl 2 = …… mol [1]
(iii) Calculate the value of x in the formula BaCl 2•xH2O.
x = …… [2]
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(e) Another student uses a different experimental method to check the value of x obtained by the method described in (b).
Give a brief description of another method, not involving titration, that could be used to determine the value of x in the formula BaCl 2•xH2O(s). Write your answer using a series of numbered steps.
Your plan should include details of the following:
• the apparatus and method you would use
• the measurements you would make.
You are provided with standard laboratory apparatus.
…… [3]
[Total: 16]
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7
Mark scheme
1(a)(i) 2.12 g 1
1(a)(ii) M1 add a (small) volume of (distilled) water (to the small beaker) 3
AND
dissolve the solid / AgNO3 (s)
M2
Transfer the solution and washings (using a funnel)
AND
into a 250 cm3 volumetric flask.
M3 Make up to the (calibration) mark / line with distilled water.
AND
then invert the (stoppered) flask (several times)
1(b)(i) (20(.0) cm3) pipette. 1
1(b)(ii) barium (ions) could react with chromate (ions). 1
1(b)(iii) Potassium chromate( VI) / K2CrO4(aq) is an irritant / corrosive 1
1(c)(i) They are (the only ones that are) concordant. 1
1(c)(ii) 2 × 0.05 1
×100 = 0.48(54%)
20.60
Correct working must be shown.
1(d)(i) 20.65 × 0.05 / 1000 = 0.00103(25) 1
1(d)(ii) = ((d)(i) / 2) *(250 / 20) 1
= (d)(i) × 6.25
1(d)(iii) M1 Mr = 1.58 / (d)(ii) 2
M2 x= (M1 – 208.3) / 18
AND
x must be an integer.
Some working must be shown.
1(e) Heat to drive off water of crystallisation. 3
M1 Apparatus
1 Bunsen burner.
2 Crucible (supported by pipeclay triangle)
M2 Measurements
1 Measure mass of crucible (+ lid) (empty).
2 Measure mass crucible (+ lid) + solid before heating
3 Measure mass of crucible (+ lid) + residue (after heating.)
M3 Key step in method
• Description of heat to constant mass.
OR
Produce a suitable precipitate using a viable reaction.
M1 Apparatus and method
• Chooses suitable reagent.
• Filter the precipitate.
• Wash and (allow to) dry
M2 Measurements
• Measure mass of hydrated barium chloride used.
• Measure mass of precipitate.
M3 Key step in method
• Description of dry to constant mass.
Effusion is the process in which a gas escapes through a small hole.
A student investigates the relationship between rate of effusion and relative molar mass of a gas using the apparatus shown in Fig. 2.1.
plunger
gas syringe
gas being tested side-arm tube
three-way tap
aluminium foil with small hole
Fig. 2.1
The following method is used:
step 1 Turn the tap and remove any gas from the syringe through the side-arm tube, by pushing in the plunger.
step 2 Add 50 cm3 of the gas being tested to the syringe through the side-arm tube.
step 3 Remove the gas from the syringe, through the side-arm tube, by pushing in the plunger.
step 4 Add 70 cm3 of the gas being tested to the syringe through the side-arm tube.
step 5 Turn the tap to connect the syringe to the tube with the aluminium foil and small hole.
step 6 Allow the syringe plunger to fall and start a timer when the volume of gas in the syringe reaches 60 cm3.
step 7 Stop the timer when the volume of gas in the syringe reaches 10 cm3. Record the time taken.
step 8 Repeat steps 1 to 7 with different gases.
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(a) Suggest why the student adds 50 cm3 of the gas being tested to the syringe in step 2 and then removes this gas in step 3.
…… [1]
(b) The student’s results are shown in Table 2.1.
Table 2.1
gas hydrogen, H2 helium, He neon, Ne argon, Ar krypton, Kr relative molar 2.0 4.0 20.2 39.9 83.8 mass, M
1
M
time taken
10.8 15.3 34.5 39.7 70.4
/s rate of
effusion
/ cm3 s–1
volume of gas rate of effusion = time taken
(i) Complete Table 2.1.
1
Give the values for to three significant figures.
M
Give the values for rate of effusion to two decimal places. [2]
(ii) Identify the dependent variable in this experiment.
…… [1]
(iii) Identify a variable, other than temperature, that is controlled when carrying out this experiment.
…… [1]
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9
1
(c) Plot a graph on the grid in Fig. 2.2 to show the relationship between rate of effusion and .
M
Use a cross (×) to plot each data point. Draw a suitable line of best fit.
5.0
4.5
4.0
3.5
3.0
2.5 rate of effusion
/ cm3 s–1
2.0
1.5
1.0
0.5
0.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
1
M
Fig. 2.2
[2]
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(d) Circle one point on the graph in Fig. 2.2 which you consider to be most anomalous.
1
Suggest one reason for this anomaly. Assume there is no error in .
M
…… [1]
(e) Graham’s law of effusion can be expressed as:
1 the rate of effusion of a gas is proportional to .
M
State whether or not the student’s results support Graham’s law of effusion.
Explain your answer, using the graph in Fig. 2.2.
…… [1]
(f) Suggest how the position of the plotted points relative to the line of best fit in Fig. 2.2 is related to the reliability of the results.
…… [1]
(g) The student then repeats this method to determine the value of M of a sample of natural gas.
The time recorded in step 7 is 31.6 s.
(i) Use the graph in Fig. 2.2 and the student’s result to calculate the value of M for this sample.
M = …… [2]
(ii) Natural gas is a mixture of mainly methane, CH4, with small amounts of other gases.
Suggest what your calculated value of the M of natural gas in (g)(i) tells you about the other gases in the mixture.
…… [1]
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11
(h) The experiment described in (g) is repeated at a higher temperature.
Suggest how the rate of effusion for this sample of natural gas would change, if at all.
Explain your answer.
effect on the rate of effusion ……
explanation ……
[1]
[Total: 14]
Important values, constants and standards
molar gas constant R = 8.31 J K–1 mol–1
Faraday constant F = 9.65 × 104 C mol–1
Avogadro constant L = 6.02 × 1023 mol–1 electronic charge e = –1.60 × 10–19 C molar volume of gas Vm = 22.4 dm3 mol–1 at s.t.p. (101 kPa and 273 K)
Vm = 24.0 dm3 mol–1 at room conditions ionic product of water Kw = 1.00 × 10–14 mol2 dm–6 (at 298 K (25 °C)) specific heat capacity of water c = 4.18 kJ kg–1 K–1 (4.18 J g–1 K–1)
The Periodic Table of Elements
Group
1 2 13 14 15 16 17 18
1 2
H He hydrogen helium
Key 1.0 4.0
3 4 atomic number 5 6 7 8 9 10
Li Be atomic symbol B C N O F Ne lithium beryllium name boron carbon nitrogen oxygen fluorine neon
6.9 9.0 relative atomic mass 10.8 12.0 14.0 16.0 19.0 20.2
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosphorus sulfur chlorine argon
DFD
23.0 24.3 3 4 5 6 7 8 9 10 11 12 27.0 28.1 31.0 32.1 35.5 39.9
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
at www.cambridgeinternational.org after the live examination series.
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton
39.1 40.1 45.0 47.9 50.9 52.0 54.9 55.8 58.9 58.7 63.5 65.4 69.7 72.6 74.9 79.0 79.9 83.8
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54
12
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon
85.5 87.6 88.9 91.2 92.9 95.9 – 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3
55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 lanthanoids
Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon
132.9 137.3 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 – – –
87 88 89–103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 actinoids
Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson
– – – – – – – – – – – – – – – – –
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium
138.9 140.1 140.9 144.2 – 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.1 175.0
89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium
– 232.0 231.0 238.0 – – – – – – – – – – –
Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download
To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge
Mark scheme
2(a) To ensure no air / other gas remains in the syringe 1
2(b)(i) 2
1
0.707 0.500 0.222 0.158 0.109
Mr
Rate of effusion /cm3s-1 4.63 3.27 1.45 1.26 0.71
2(b)(ii) Time (taken). 1
2(b)(iii) size of hole 1
2(c) M1 all 5 points plotted correctly. 2
M2 Straight line of best fit drawn
2(d) Point most anomalous to the plotted line of best fit circled. 1
AND
If point above LOBF
(Measured rate of effusion is higher than the true rate predicted by LOBF.)
for this point …
measured / recorded (effusion) time < true / actual time
OR
If point below LOBF
(Measured rate of effusion is lower than the true rate predicted by LOBF.)
for this point …
measured / recorded (effusion) time > true / actual time
2(e) Yes AND The graph / LOBF… 1
is a straight-line AND it goes through the origin.
2(f) The results are not reliable as there is an anomalous result. 1
2(g)(i) M1 Effusion rate = 50/31.6 = (1.58) 1
1
Correct value for read from x-axis
Mr
M2 Value correctly converted to M. 1
2(g)(ii) If calculated M > 16 1
(The average) M (of the other components) is greater than 16 / calculated value for g(i).
2(h) (Rate of effusion) increases 1
AND
(At higher temperature) gas particles move more quickly.
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Chemistry 9701/53 for October/November 2025 is out of 30 marks, with 1 hour 15 minutes to answer it, across 2 questions.
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