Cambridge Assessment International Education
Cambridge Ordinary Level
CHEMISTRY 5070/32
Paper 3 Practical Test May/June 2018
MARK SCHEME
Maximum Mark: 40
Published
This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the
examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the
details of the discussions that took place at an Examiners’ meeting before marking began, which would have
considered the acceptability of alternative answers.
Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for
Teachers.
Cambridge International will not enter into discussions about these mark schemes.
Cambridge International is publishing the mark schemes for the May/June 2018 series for most
Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and
some Cambridge O Level components.
IGCSE™ is a registered trademark.
This document consists of 7 printed pages.
© UCLES 2018 [Turn over
,5070/32 Cambridge O Level – Mark Scheme May/June 2018
PUBLISHED
Generic Marking Principles
These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.
GENERIC MARKING PRINCIPLE 1:
Marks must be awarded in line with:
• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.
GENERIC MARKING PRINCIPLE 2:
Marks awarded are always whole marks (not half marks, or other fractions).
GENERIC MARKING PRINCIPLE 3:
Marks must be awarded positively:
• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.
GENERIC MARKING PRINCIPLE 4:
Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.
© UCLES 2018 Page 2 of 7
,5070/32 Cambridge O Level – Mark Scheme May/June 2018
PUBLISHED
GENERIC MARKING PRINCIPLE 5:
Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).
GENERIC MARKING PRINCIPLE 6:
Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.
© UCLES 2018 Page 3 of 7
, 5070/32 Cambridge O Level – Mark Scheme May/June 2018
PUBLISHED
Question Answer Marks
1(a) Titration 12
Measurements (1)
Both readings, i.e. initial and final are present for each titration and readings are recorded to 1dp, no reading is in excess of
50.0 and no initial reading is given as 50.0
Titres (1)
All the titres are calculated correctly, i.e. no subtraction errors.
Accuracy (6)
For the two best titres give:
3 marks for a titre within 0.2 cm3 of the Supervisor’s value.
2 marks for a titre within 0.3 cm3 of the Supervisor’s value.
1 mark for a titre within 0.4 cm3 of the Supervisor’s value.
Concordance (3)
Give 3 marks if all the ticked values are within 0.2 cm3.
Give 2 marks if all the ticked values are within 0.3 cm3.
Give 1 marks if all the ticked values are within 0.4 cm3.
Average (1)
Give 1 mark if the candidate calculates a correct average of selected titres.
1(b) Pipette volume = 25 cm3 and assuming average volume of P used = 25.2 cm3 2
Concentration of hydrogen ions in P
= (25.0 × 0.225 × 2) / 25.2 (1)
= 0.446 mol / dm3 (1)
1(c) Moles of hydrogen ions in 1 dm3 of P due to sulfuric acid 1
= (b) – 0.125
= 0.446 – 0.125
= 0.321
© UCLES 2018 Page 4 of 7
Cambridge Ordinary Level
CHEMISTRY 5070/32
Paper 3 Practical Test May/June 2018
MARK SCHEME
Maximum Mark: 40
Published
This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the
examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the
details of the discussions that took place at an Examiners’ meeting before marking began, which would have
considered the acceptability of alternative answers.
Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for
Teachers.
Cambridge International will not enter into discussions about these mark schemes.
Cambridge International is publishing the mark schemes for the May/June 2018 series for most
Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and
some Cambridge O Level components.
IGCSE™ is a registered trademark.
This document consists of 7 printed pages.
© UCLES 2018 [Turn over
,5070/32 Cambridge O Level – Mark Scheme May/June 2018
PUBLISHED
Generic Marking Principles
These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the
specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these
marking principles.
GENERIC MARKING PRINCIPLE 1:
Marks must be awarded in line with:
• the specific content of the mark scheme or the generic level descriptors for the question
• the specific skills defined in the mark scheme or in the generic level descriptors for the question
• the standard of response required by a candidate as exemplified by the standardisation scripts.
GENERIC MARKING PRINCIPLE 2:
Marks awarded are always whole marks (not half marks, or other fractions).
GENERIC MARKING PRINCIPLE 3:
Marks must be awarded positively:
• marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the
scope of the syllabus and mark scheme, referring to your Team Leader as appropriate
• marks are awarded when candidates clearly demonstrate what they know and can do
• marks are not deducted for errors
• marks are not deducted for omissions
• answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the
question as indicated by the mark scheme. The meaning, however, should be unambiguous.
GENERIC MARKING PRINCIPLE 4:
Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level
descriptors.
© UCLES 2018 Page 2 of 7
,5070/32 Cambridge O Level – Mark Scheme May/June 2018
PUBLISHED
GENERIC MARKING PRINCIPLE 5:
Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may
be limited according to the quality of the candidate responses seen).
GENERIC MARKING PRINCIPLE 6:
Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or
grade descriptors in mind.
© UCLES 2018 Page 3 of 7
, 5070/32 Cambridge O Level – Mark Scheme May/June 2018
PUBLISHED
Question Answer Marks
1(a) Titration 12
Measurements (1)
Both readings, i.e. initial and final are present for each titration and readings are recorded to 1dp, no reading is in excess of
50.0 and no initial reading is given as 50.0
Titres (1)
All the titres are calculated correctly, i.e. no subtraction errors.
Accuracy (6)
For the two best titres give:
3 marks for a titre within 0.2 cm3 of the Supervisor’s value.
2 marks for a titre within 0.3 cm3 of the Supervisor’s value.
1 mark for a titre within 0.4 cm3 of the Supervisor’s value.
Concordance (3)
Give 3 marks if all the ticked values are within 0.2 cm3.
Give 2 marks if all the ticked values are within 0.3 cm3.
Give 1 marks if all the ticked values are within 0.4 cm3.
Average (1)
Give 1 mark if the candidate calculates a correct average of selected titres.
1(b) Pipette volume = 25 cm3 and assuming average volume of P used = 25.2 cm3 2
Concentration of hydrogen ions in P
= (25.0 × 0.225 × 2) / 25.2 (1)
= 0.446 mol / dm3 (1)
1(c) Moles of hydrogen ions in 1 dm3 of P due to sulfuric acid 1
= (b) – 0.125
= 0.446 – 0.125
= 0.321
© UCLES 2018 Page 4 of 7
