Chemistry A Level 6 Markers – Practicals Exam with Questions and Answers –
100% Solved
Describe how you would carry out an experiment to determine the enthalpy of solution of
anhydrous magnesium chloride. You should use about 0.8 g of anhydrous magnesium chloride.
Explain how your results could be used to calculate the enthalpy of solution. - ✔✔✔-Stage 1
Method
(1a) Measures water with named appropriate apparatus (1b) Suitable volume/mass /
volume/mass in range 10 - 200 cm3 /g
(1c) Into insulated container / polystyrene cup (NOT just 'lid')
(1d) Add known mass of MgCl2(s) (1e) Use of 'before and after' weighing method. NOT 'added
with washings' Stage 2 Measurements (could mark from diagram)
(2a) Record initial temperature (min 2 measurements) (2b) Record T at regular timed intervals
for 5+ mins / until trend seen
(2c) Plot T vs time
Stage 3 Use of Results
(3a and 3b could come from diagram)
(3a) Extrapolate lines to when solid added (to find initial and final T)
(3b) Tfinal - Tinitial = ∆T / idea of finding ∆T from graph at point of addition
(3c) q = mc∆T (3d) amount = mass/Mr (0.80/95.3 = 8.39 x 10-3 mol) (3e) ∆Hsoln = q/8.39 x 10-3
or in words
Explain the bonding in and the shape of a benzene molecule. Compare the stability of benzene
with that of the hypothetical cyclohexa-1,3,5-triene molecule. Use the data in your answer -
✔✔✔-Stage 1 Bonding
1a) Each C has three (covalent) bonds
1b) Spare electrons (in a p orbital) overlap (to form a cloud)
1c) delocalisation
Stage 2 Shape
2a) Planar
2b) Hexagon/6 carbon ring/120o bond angle
, Chemistry A Level 6 Markers – Practicals Exam with Questions and Answers –
100% Solved
2c) C-C bonds equal in length / C-C bond lengths between single and double bond
Stage 3 Stability
3a) Expected H o hydrogn of cyclohexatriene = -360 kJ mol-1
3b) H o hydrogn benzene (is less exothermic) by 152 kJ mol-1
3c) Benzene lower in energy than cyclohexatriene / Benzene is more stable
Explain, giving brief experimental details, how you could use a series of experiments to
determine the order of this reaction with respect to A. In each experiment you should obtain a
measure of the initial rate of reaction. - ✔✔✔-Stage 1 Preparation
1a Measure (suitable/known volumes of) some reagents (ignore quoted values for volume)
1b Measure (known amount of) X / use a colorimeter
1c into separate container(s) - (allow up to two reagents and X measured together into one
container); reference to A, B or C added last. NOT if X added last.
Stage 2 Procedure
2a Start clock/timer at the point of mixing (don't allow if only 2 reagents mixed) (allow even if X
not added or added last)l
2b Time recorded for appearance of blue colour/specific reading on colorimeter/disappearing
cross
2c Use of same concentration of B and C / same total volume / same volume/amount of X
2d Same temperature/use water bath
2e Repeat with different concentrations of A (can be implied through different volumes of A and
same total volume)
Stage 3 Use of Results
3a 1/time taken is a measure of the rate
3b plot of 1/time against volumes/concentrations of A or plot log(1/time) vs log(volume or
concentration of A)
100% Solved
Describe how you would carry out an experiment to determine the enthalpy of solution of
anhydrous magnesium chloride. You should use about 0.8 g of anhydrous magnesium chloride.
Explain how your results could be used to calculate the enthalpy of solution. - ✔✔✔-Stage 1
Method
(1a) Measures water with named appropriate apparatus (1b) Suitable volume/mass /
volume/mass in range 10 - 200 cm3 /g
(1c) Into insulated container / polystyrene cup (NOT just 'lid')
(1d) Add known mass of MgCl2(s) (1e) Use of 'before and after' weighing method. NOT 'added
with washings' Stage 2 Measurements (could mark from diagram)
(2a) Record initial temperature (min 2 measurements) (2b) Record T at regular timed intervals
for 5+ mins / until trend seen
(2c) Plot T vs time
Stage 3 Use of Results
(3a and 3b could come from diagram)
(3a) Extrapolate lines to when solid added (to find initial and final T)
(3b) Tfinal - Tinitial = ∆T / idea of finding ∆T from graph at point of addition
(3c) q = mc∆T (3d) amount = mass/Mr (0.80/95.3 = 8.39 x 10-3 mol) (3e) ∆Hsoln = q/8.39 x 10-3
or in words
Explain the bonding in and the shape of a benzene molecule. Compare the stability of benzene
with that of the hypothetical cyclohexa-1,3,5-triene molecule. Use the data in your answer -
✔✔✔-Stage 1 Bonding
1a) Each C has three (covalent) bonds
1b) Spare electrons (in a p orbital) overlap (to form a cloud)
1c) delocalisation
Stage 2 Shape
2a) Planar
2b) Hexagon/6 carbon ring/120o bond angle
, Chemistry A Level 6 Markers – Practicals Exam with Questions and Answers –
100% Solved
2c) C-C bonds equal in length / C-C bond lengths between single and double bond
Stage 3 Stability
3a) Expected H o hydrogn of cyclohexatriene = -360 kJ mol-1
3b) H o hydrogn benzene (is less exothermic) by 152 kJ mol-1
3c) Benzene lower in energy than cyclohexatriene / Benzene is more stable
Explain, giving brief experimental details, how you could use a series of experiments to
determine the order of this reaction with respect to A. In each experiment you should obtain a
measure of the initial rate of reaction. - ✔✔✔-Stage 1 Preparation
1a Measure (suitable/known volumes of) some reagents (ignore quoted values for volume)
1b Measure (known amount of) X / use a colorimeter
1c into separate container(s) - (allow up to two reagents and X measured together into one
container); reference to A, B or C added last. NOT if X added last.
Stage 2 Procedure
2a Start clock/timer at the point of mixing (don't allow if only 2 reagents mixed) (allow even if X
not added or added last)l
2b Time recorded for appearance of blue colour/specific reading on colorimeter/disappearing
cross
2c Use of same concentration of B and C / same total volume / same volume/amount of X
2d Same temperature/use water bath
2e Repeat with different concentrations of A (can be implied through different volumes of A and
same total volume)
Stage 3 Use of Results
3a 1/time taken is a measure of the rate
3b plot of 1/time against volumes/concentrations of A or plot log(1/time) vs log(volume or
concentration of A)
