Chemistry 9701/54 May/June 2025: question paper and mark scheme
Cambridge AS & A Level Chemistry (9701), Paper 5 Planning, Analysis and Evaluation, May/June 2025. Read both free below, or download them. Done the paper? Get it marked by AI against this mark scheme.
The relative molecular mass, Mr , of an unknown volatile liquid, Y, can be determined experimentally.
A student uses the following method to determine the volume of a conical flask.
step 1 Weigh a dry conical flask.
step 2 Fill the conical flask completely with distilled water.
step 3 Weigh the conical flask when filled with distilled water.
step 4 Use a thermometer to measure the temperature of the distilled water in the conical flask.
The student collects the results shown in Table 1.1.
Table 1.1
mass of dry flask / g 31.022 mass of flask filled with water / g 161.175 temperature of water in flask / °C 23.0 laboratory atmospheric pressure / kPa 99.0
(a) Fig. 1.1 shows the variation of the density of water with temperature.
1.000
0.999
0.998
density
/ g cm–3
0.997
0.996
0.995
16 18 20 22 24 26 28 30
temperature / °C
Fig. 1.1
(i) Use Fig. 1.1 to determine the density of water at 23.0 °C.
Give your answer to four decimal places.
density of water = …… g cm–3 [1]
(ii) Calculate the volume of the flask, using the density of water determined in (a)(i).
volume of flask = …… cm3 [2]
(b) Another student determines the volume of a different conical flask to be 129.56 cm3. This conical flask is used to determine the Mr of unknown volatile liquid Y.
The following method is used.
step 1 Cover the opening of the dry conical flask with aluminium foil and secure using a rubber band.
step 2 Weigh the conical flask, aluminium foil and rubber band. Record the mass.
step 3 Use a syringe with a needle to make a small hole in the aluminium foil and inject approximately 5 cm3 of Y into the conical flask. Remove the syringe.
step 4 Place the conical flask in a water-bath containing boiling water.
step 5 Allow all of Y to evaporate. Keep the conical flask containing vaporised Y in the boiling water for a further 3 minutes.
step 6 Carefully remove the conical flask from the boiling water and dry the outside surface thoroughly.
step 7 Weigh the conical flask, aluminium foil, rubber band and contents. Record this mass.
(i) Suggest why the conical flask containing vaporised Y is kept in boiling water for 3 minutes in step 5.
…… [1]
(ii) Suggest why it is not necessary to determine the mass of liquid Y injected into the conical flask by the syringe in step 3.
…… [1]
(iii) The student thinks that Y is toxic. Other than wearing safety glasses and a lab coat, state one safety precaution that must be taken when carrying out this experiment.
…… [1]
(c) Table 1.2 shows the student’s results.
Table 1.2
temperature of water-bath / °C 100.0
laboratory atmospheric pressure / kPa 99.0
mass of conical flask, aluminium foil and rubber band
31.123
measured in step 2 / g mass of conical flask, aluminium foil, rubber band and
31.429
Y measured in step 7 / g
mass of Y in flask in step 7 / g 0.306
volume of conical flask used / cm3 129.56
(i) Calculate the percentage error in the mass measured in step 2.
Show your working.
percentage error = …… [1]
(ii) The student assumes that the vapour formed from liquid Y is an ideal gas. The ideal gas equation is shown.
pV = nRT
p = pressure of gas measured in Pa
V = volume of gas in m3 n = number of moles of gas
R = molar gas constant
T = temperature in K
Use the ideal gas equation and the results in Table 1.2 to calculate the amount, in mol, of
Y in the conical flask in step 7.
Assume that the temperature of the vapour formed from liquid Y is 100 °C.
amount of Y = …… mol [2]
(iii) Calculate the Mr of Y.
Mr of Y = …… [1]
(d) The actual temperature of the vapour formed from liquid Y is less than 100 °C. Describe and
explain the effect this has on the calculated value of the Mr .
effect on calculated Mr ……
explanation ……
[1]
(e) The boiling point of methylbenzene is 111 °C.
Suggest why the Mr of methylbenzene cannot be determined using this method.
…… [1]
[Total: 12]
Mark scheme
1(a)(i) 0.9976 (g cm–3) 1
1(a)(ii) M1 mass of water = 161.175 – 31.022 g = 130.153 g 2
M2 volume = mass of water / density in (a)(i) = 130.153 / 0.9976 = 130.466 (cm3)
1(b)(i) to ensure the vapour (Y) (in the conical flask) has reached the temperature (of the boiling water / 100 °C) 1
1(b)(ii) mass of vapour (occupying flask)(at step 7) is used in calculation 1
1(b)(iii) (perform the experiment in a) fume hood 1
1(c)(i) ( 0.0005 × 2) ×100 = 3.21 × 10–3 (%) 1
31.123
1(c)(ii) M1 correct value and units used for each quantity 2
• 99000 Pa
• 1.2956 × 10–4 m3 (129.56 × 10–6)
• 373 K (273 +100)
M2 rearranges equation to give n=pV / RT AND correct evaluation
99000 ×129.56 ×10−6
n=
8.31×373
= 4.138055 × 10–3 (mol)
1(c)(iii) Mr = 0.306 / (c)(ii) = 73.94778 1
1(d) (calculated Mr would be) greater (than true value) 1
AND
mass of vapour measured is greater (all other measurements are the same)
1(e) temperature (of water bath) not high enough (to boil methylbenzene) 1
A student carries out an experiment to determine the charge of an aqueous ion, Mn+(aq), of metal M.
The student prepares 100.0 cm3 of 1.00 mol dm–3 aqueous copper(II) nitrate, Cu(NO3)2(aq), to use in the experiment.
(a) Calculate the mass of Cu(NO3)2•3H2O(s) required to prepare 100.0 cm3 of 1.00 mol dm–3
Cu(NO3)2(aq).
mass = …… g [1]
(b) Describe the steps the student should take to prepare 100.0 cm3 of 1.00 mol dm–3
Cu(NO3)2(aq) starting from the mass calculated in (a) supplied in a small beaker.
Give the name and capacity of any apparatus used.
Write your answer using a series of numbered steps.
…… [3]
(c) The student sets up the electrochemical cell shown in Fig. 2.1 to investigate the effect of changing the concentration of Mn+(aq) on the measured cell potential, Ecell.
high-resistance voltmeter
V
M(s) electrode A Cu(s) electrode
Mn+(aq) 1.00 mol dm–3
Cu(NO3)2(aq)
Fig. 2.1
Suggest the function of the item labelled A in Fig. 2.1.
…… [1]
(d) The student uses the apparatus in Fig. 2.1 to measure the cell potentials, using six solutions each with a different concentration of Mn+(aq).
Table 2.1 shows the results obtained by the student.
Table 2.1
electrode concentration cell potential, potential of of Mn+(aq) log [Mn+]
Ecell / V Mn+(aq) / M(s)
/ mol dm–3
/V
1.00 × 10–2 3.295 –2.00
5.00 × 10–3 3.304 –2.30
1.00 × 10–3 3.325 –3.00
5.00 × 10–4 3.343 –3.30
1.00 × 10–4 3.354 –4.00
1.00 × 10–5 3.384 –5.00
electrode potential of Mn+(aq) / M(s) = ECu – Ecell
electrode potential of Cu2+(aq) / Cu(s), ECu = 0.337 V
Complete Table 2.1. Record your values to three decimal places.
[1]
(e) Identify the independent variable in this experiment.
…… [1]
(f) (i) Plot a graph on the grid in Fig. 2.2 to show the relationship between the electrode potential of Mn+(aq) / M(s) and log [Mn+]. Use a cross (×) to plot each data point. Draw a straight line of best fit.
–2.94
–2.96
–2.98
electrode potential of
Mn+(aq) / M(s) / V –3.00
–3.02
–3.04
–3.06
–5 –4 –3 –2 log [Mn+]
Fig. 2.2
[2]
(ii) Circle the one point on the graph that you consider to be most anomalous.
Suggest one reason why this anomaly may have occurred during the experimental procedure. Assume no error was made in the measurement of the cell potential.
…… [1]
(iii) Suggest how the reliability of the data shown in Table 2.1 could be improved.
…… [1]
(g) (i) Use Fig. 2.2 to determine the gradient of the line of best fit.
State the coordinates of both points you used in your calculation. These must be selected from your line of best fit. Give the gradient to three significant figures.
coordinates 1 …… coordinates 2 ……
gradient = …… [2]
(ii) For the electrode equilibrium,
M(s) Mn+(aq) + ne–,
the Nernst equation can be written as shown.
2.303 RT
E = Eo + log [Mn+]
nF
E = electrode potential
E o = standard electrode potential
R = molar gas constant
T = temperature in K
F = Faraday constant
The equation for a straight line is y = mx + c.
State which parts in the Nernst equation correspond to y, m and c.
y = ……
m = ……
c = ……
[3]
(iii) Use the value that you calculated for the gradient of your line of best fit in (g)(i) and the
Nernst equation to calculate the value of n in Mn+(aq).
The experiment is carried out at 25.0 °C.
(If you were unable to determine an answer to (g)(i), then use the value 0.0285 for the gradient. This is not the correct value.)
n = …… [2]
[Total: 18]
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
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) 24.15 (g) 1
2(b) M1 add a (small) volume of (distilled) water (to the small beaker) 3
AND
dissolve the solid / Cu(NO3)2⦁3H2O(s)
M2 transfer the solution to a 100 cm3 volumetric flask with washings
M3 make up to the (calibration) mark / line (with distilled water)
AND
invert the (stoppered) flask (to mix)
2(c) to allow ion(s) to move (between half-cells / two beakers) 1
2(d) 1
log [Mn+] electrode potential
of Mn+(aq) / M(s)
/V
–2.00 –2.958
–2.30 –2.967
–3.00 –2.988
–3.30 –3.006
–4.00 –3.017
–5.00 –3.047
2(e) concentration of Mn+ ((aq)) 1
2(f)(i) M1 points plotted correctly 2
M2 straight line of best fit drawn
2(f)(ii) point most anomalous to the plotted line of best fit circled 1
AND
the actual concentration of the solution was lower than recorded value (5.00 × 10–4)
2(f)(iii) repeat the procedure for the solution giving an anomalous result 1
2(g)(i) M1 two acceptable coordinates from line of best fit expressed in the form (x,y) 2
M2 gradient correctly calculated from points listed for M1 to three significant figures
2(g)(ii) y=E 3
m = 2.303RT / nF
c = E⦵
2(g)(iii) M1 correct rearrangement AND values 2
2.303 ×8.31× 298
n=
gradient×9.65 ×104
M2 correctly calculated value rounded to whole number
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Chemistry 9701/54 for May/June 2025 is out of 30 marks, with 1 hour 15 minutes to answer it, across 2 questions.
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