Q14.
(a) M1 Amount ZnSO4 = 1.0 × 
mol or Amount ZnSO4 = 0.050 mol
Mark M1 and M2 independently
1
M2 Amount Mg = 
mol or Amount Mg = 0.0856 mol
(Hence Mg in excess)
1
M3 Q = mcΔT
M3 could be scored in M4
1
M4 Q = 50.0 × 4.18 × 37.3
or Q = 7795.7 J
If an error in M4, lose M4 and M5 and only award M6 for correct use of their incorrect M4 and division by their correct limiting reagent
1
M5 (Energy released per mole) 
kJ mol−1 or 
J mol−1
M5 division by their limiting reagent
1
M6 ΔH = − 156 kJ mol−1
1
(b) Heat loss (from the apparatus would mean the experimental value is smaller / lower / less exothermic than the data source)
1
(c) Marks awarded for this answer will be determined by the quality of the communication as well as the standard of the scientific response. Examiners should apply a ‘best-fit’ approach to the marking.
Level 3 (5 – 6 marks)
Covers 3 Stages with matching justifications
Answer is full and detailed and is supported by an appropriate range of relevant points such as those given below:
• argument is well structured with minimum repetition or irrelevant points
• accurate and clear expression of ideas with only minor errors in the use of technical terms, spelling and punctuation and grammar
Level 2 (3 – 4 marks)
Covers 2 Stages with matching justification. OR covers 3 Stages with incomplete justification
Answer has some omissions but is generally supported by some of the relevant points below:
• the argument shows some attempt at structure
• the ideas are expressed with reasonable clarity but with a few errors in the use of technical terms, spelling, punctuation and grammar
Level 1 (1 – 2 marks)
Covers 1 Stage with matching justification. OR covers 2 Stages with incomplete justification
Answer is largely incomplete. It may contain valid points which are not clearly linked to an argument structure. Unstructured answer. Errors in the use of technical terms, spelling, punctuation and grammar or lack of fluency
Level 0 (0 marks)
Insufficient correct chemistry
Indicative Chemistry Content
Stage 1 Improved insulation
1a Insulate the beaker or use a polystyrene cup or a lid
1b To reduce heat loss
Stage 2 Improved temperature recording
2a Record the temperature for a suitable time before adding the metal
2b To establish an accurate initial temperature
OR
2c Record temperature values at regular time intervals
2d To plot the temperature results against time on a graph
Stage 3 Improved analysis of results
3a Extrapolate the cooling back to the point of addition
3b To establish a (theoretical) maximum temperature OR temperature change (e.g. at the 4th minute) OR adjust for the cooling /apply a cooling correction
3a and 3b could be seen on an extrapolated sketch graph
(Note– IGNORE use of measuring equipment with greater precision)
6
[13]