EXAMPRO
AqA
A-LEVEL CHEMISTRY MARK SCHEME
Practice Paper 1 Maximum marks: 105
View detailed guidance on the conclusions you can draw from your students' performance in
these papers on the MERiT welcome page. Understand how your students compare with
others and target revision effectively by entering marks into MERiT.
1 (a) (i) [H+][OH -J OR (H3O+][OH-J 1
Ignore (aq)
Must have [ J not ()
(ii) ✓3.46 X 10-14 (= 1.86 X 10-7) 2
If no square root, CE= 0
pH= 6.73 Must be 2dp
(iii) [H = 10-1136 (= 4 .365 X 10-12 OR 4.37 X 10-12)
+] 1
Mark for working
Kw= [4.365 x 10-12 OR 4.37 x 10-12 x 0.047] = 2.05 x 10-13 1
Allow 2.05 x 10-13 - 2.1 x 10-13
Mark for answer
Ignore units
(b) (i) HCOOH Hcoo-+ w 1
Must have �=====� but ignore brackets.
OR HCOOH + H2O
Allow HCO2- or CHOO- ie minus must be on oxygen, so
penalise COOH-
(ii) Ka = [w ][Hcoo-] O
R [H 3 0� ][Hcoo-] 1
HCOOH HCOOH
Must have all brackets but allow ()
Must be HCOOH etc.
Allow ecf in formulae from (b)(i)
(iii) M1 1
}��g ([w ) 2 = 1.78 x 10-� x 0.056 = 9.97 x 10-e)
[ HJ
Ka =
Allow HA or HX etc.
✓
Allow [WJ= (Ka x [HA]) for M1
M2 [H+] = 3.16 x 10-3 1
Mark for answer
M3 pH= 2.50 allow more than 2 dp but not fewer 1
Allow correct pH from their wrong [WJ here only If square root
shown but not taken, pH= 5.00 can score max 2 for M1 and M3
Page 1
, (iv) M1 Decrease Mark M1 independently 1
M2 Eqm shifts / moves to RHS OR more H+ OR Ka increases 1
OR more dissociation
M3 To reduce temperature or oppose increase / change in temperature 1
Only award M3 following correct M2
(c) (i) M1 1
If [HX]/[X-] upside down, no marks
M2 1
(= 2.27 × 10−4)
M3 pH = 3.64 allow more than 2 dp but not fewer 1
pH calc NOT allowed from their wrong [H+] here
(ii) M1 Mol H+ added = 5.00 × 10−4 1
Mark on from AE in moles of HCl (eg 5 × 10−3 gives pH =
3.42 scores 3)
M2 Mol HCOOH = 2.40 × 10−2 and Mol HCOO– = 1.79 × 10−2 1
If either wrong no further marks except AE (−1) OR if ECF in
mol acid and / or mol salt from (c)(i), can score all 4
M3 1
If [HX]/[X-] upside down here after correct expression in (c)(i),
no further marks
If [HX]/[X-] upside down here and is repeat error from (c)(i), max
3 (pH = 3.88 after 3.86 in (c)(i))
M4 pH = 3.62 allow more than 2 dp but not fewer 1
pH calc NOT allowed from their wrong [H+] here
[Total 20 marks]
2 (a) Variable / many oxidation states 1
(b) V2O5 + SO2 → V2O4 + SO3 1
Equations can be in either order
Allow multiples
V2O4 + ½O2 → V2O5 1
(c) (i) In a different phase / state from reactants 1
(ii) Impurities poison / deactivate the catalyst / block the active sites 1
Allow (adsorbs onto catalyst AND reduces surface area)
(d) (i) The catalyst is a reaction product 1
(ii) Mn2+ / Mn3+ ion(s) 1
(iii) 4Mn2+ + MnO4− + 8H+ → 5Mn3+ + 4H2O 1
Equations can be in either order
2Mn3+ + C2O42− → 2Mn2+ + 2CO2 1
[Total 9 marks]
AqA
A-LEVEL CHEMISTRY MARK SCHEME
Practice Paper 1 Maximum marks: 105
View detailed guidance on the conclusions you can draw from your students' performance in
these papers on the MERiT welcome page. Understand how your students compare with
others and target revision effectively by entering marks into MERiT.
1 (a) (i) [H+][OH -J OR (H3O+][OH-J 1
Ignore (aq)
Must have [ J not ()
(ii) ✓3.46 X 10-14 (= 1.86 X 10-7) 2
If no square root, CE= 0
pH= 6.73 Must be 2dp
(iii) [H = 10-1136 (= 4 .365 X 10-12 OR 4.37 X 10-12)
+] 1
Mark for working
Kw= [4.365 x 10-12 OR 4.37 x 10-12 x 0.047] = 2.05 x 10-13 1
Allow 2.05 x 10-13 - 2.1 x 10-13
Mark for answer
Ignore units
(b) (i) HCOOH Hcoo-+ w 1
Must have �=====� but ignore brackets.
OR HCOOH + H2O
Allow HCO2- or CHOO- ie minus must be on oxygen, so
penalise COOH-
(ii) Ka = [w ][Hcoo-] O
R [H 3 0� ][Hcoo-] 1
HCOOH HCOOH
Must have all brackets but allow ()
Must be HCOOH etc.
Allow ecf in formulae from (b)(i)
(iii) M1 1
}��g ([w ) 2 = 1.78 x 10-� x 0.056 = 9.97 x 10-e)
[ HJ
Ka =
Allow HA or HX etc.
✓
Allow [WJ= (Ka x [HA]) for M1
M2 [H+] = 3.16 x 10-3 1
Mark for answer
M3 pH= 2.50 allow more than 2 dp but not fewer 1
Allow correct pH from their wrong [WJ here only If square root
shown but not taken, pH= 5.00 can score max 2 for M1 and M3
Page 1
, (iv) M1 Decrease Mark M1 independently 1
M2 Eqm shifts / moves to RHS OR more H+ OR Ka increases 1
OR more dissociation
M3 To reduce temperature or oppose increase / change in temperature 1
Only award M3 following correct M2
(c) (i) M1 1
If [HX]/[X-] upside down, no marks
M2 1
(= 2.27 × 10−4)
M3 pH = 3.64 allow more than 2 dp but not fewer 1
pH calc NOT allowed from their wrong [H+] here
(ii) M1 Mol H+ added = 5.00 × 10−4 1
Mark on from AE in moles of HCl (eg 5 × 10−3 gives pH =
3.42 scores 3)
M2 Mol HCOOH = 2.40 × 10−2 and Mol HCOO– = 1.79 × 10−2 1
If either wrong no further marks except AE (−1) OR if ECF in
mol acid and / or mol salt from (c)(i), can score all 4
M3 1
If [HX]/[X-] upside down here after correct expression in (c)(i),
no further marks
If [HX]/[X-] upside down here and is repeat error from (c)(i), max
3 (pH = 3.88 after 3.86 in (c)(i))
M4 pH = 3.62 allow more than 2 dp but not fewer 1
pH calc NOT allowed from their wrong [H+] here
[Total 20 marks]
2 (a) Variable / many oxidation states 1
(b) V2O5 + SO2 → V2O4 + SO3 1
Equations can be in either order
Allow multiples
V2O4 + ½O2 → V2O5 1
(c) (i) In a different phase / state from reactants 1
(ii) Impurities poison / deactivate the catalyst / block the active sites 1
Allow (adsorbs onto catalyst AND reduces surface area)
(d) (i) The catalyst is a reaction product 1
(ii) Mn2+ / Mn3+ ion(s) 1
(iii) 4Mn2+ + MnO4− + 8H+ → 5Mn3+ + 4H2O 1
Equations can be in either order
2Mn3+ + C2O42− → 2Mn2+ + 2CO2 1
[Total 9 marks]
