OCR Chemistry A-Level Redox
OCR Chemistry A-Level Redox
OCR Chemistry A-Level Redox
A-Level
CHEMISTRY
Foundations In Chemistry
Redox
Time allowed
47 minutes
MARK SCHEME
Score Percentage
/39 %
4.1 | CELL BIOLOGY | QUESTION PAPER 1 1
1. (i) O goes from –2 to 0
Oxidation numbers may be seen with equation
N goes from +5 to +4
N is reduced AND O is oxidised
Third mark is dependent upon seeing a reduction in oxidation
number of N and an increase in oxidation number of O
ALLOW ECF for third mark for N is oxidised and O is reduced
if incorrect oxidation numbers support this
IGNORE references to strontium
IGNORE references to electron loss OR gain
DO NOT ALLOW ‘One increases and one decreases’
3
Plymstock School 1
2. (i) Mg
oxidation number changes from 0 to (+)2
OR oxidation number increases by 2
ALLOW correct oxidation numbers shown in equation
2nd mark is dependent on identification of Mg
IGNORE electrons
2
Plymstock School 2
5. (i) loss (of electrons) 1
(ii) Ba
0 → (+)2 (accept 2+) 2
[3]
Mg
(b) NaClO3 1
[6]
Plymstock School 3
(b) In Ca, oxidation state = 0 and 2
In CaCl2, oxidation state = +2
Oxidation number increases from Ca to CaCl2
[4]
9. (a) RaCl2 1
Plymstock School 4