AS AQA chemistry paper 2 Exam
2024/2025
/Explain, in general terms, how a catalyst increases the rate of a reaction. - Answer-
provides a different route
With lower activation energy
/.Explain, in terms of collision theory, the effect of increasing the concentration of
hydrogen peroxide on the rate of reaction. - Answer-more moles in given volume
so successful collisions are more frequent
/.State why the student should use sodium hydroxide solution rather than water for the
final rinse of the burette. - Answer-use of water would dilute the NaOH
/.The total uncertainty when using the burette is ±0.15 cm3.
Using 23.95 as mean titre calculate % uncertainty - Answer-(0..95) x 100%
= 0.63
/.find the mass, in mg, of citric acid dissolved in 250 cm3 of the solution.
The relative molecular mass (Mr) of citric acid is 192.0.
Volume = 23.95 cm3 - Answer-moles NaOH = 23. x 0.0500
moles NaOH = 0.001198
moles acid in flask = 0.001198/3 titres x 10
moles acid in flask = 0.003992
mass acid = 0.003992 x 192.0 = 0.766 g
Mass acid = 766 (mg)
/.Calculate the percentage purity of this sample of citric acid. - Answer-(766/784 x 100 )
= 97.7
/.When ethanoic acid reacts with sodium hydroxide, the enthalpy change, ∆H, is -56.1
kJ mol-1
CH3COOH(aq) + NaOH(aq) ⟶CH3COONa(aq) + H2O(l)
Calculate the temperature rise when 25 cm3 of 2.0 mol dm-3 aqueous ethanoic acid
react with 25 cm3 of 2.0 mol dm-3 aqueous sodium hydroxide.
Assume that both solutions have the same initial temperature, have a density of 1.0 g
cm-3 and a specific heat capacity of 4.18 J K-1 g-1 - Answer-moles ( = 25/1000 x 2.0) =
0.050
, heat released = 0.050 x 56.1
heat released = 2.805 kJ
delta T = q / mc
delta T == 2805 50 x 4.18
delta T = 13.4 C
/.State the general formula of an alkane containing n carbon atoms. Deduce an
expression for the relative molecular mass (Mr) of an alkane in terms of n. - Answer-
General formula = CnH2n+2
Expression = 14.0n + 2.0 or 14n + 2
/.Explain why nonane has a higher boiling point than 2,4-dimethylheptane. - Answer-
nonane has stronger van der Waals' forces between molecules
Due to nonane molecules pack closer together
/.Nonane is often found in fuel for jet engines. Combustion in jet engines produces
pollutants including nitrogen monoxide (NO).
Explain how this nitrogen monoxide is formed - Answer-nitrogen and oxygen from air
react at high temperature
/.Give an equation for the complete combustion of nonane. - Answer-C9H20 + 14O2
9CO2 + 10H2O
/.Nonane can be cracked to form large quantities of propene.
Name the type of cracking used. - Answer-thermal cracking
/.A hydrocarbon contains 87.8% by mass of carbon and has a relative molecular mass
(Mr) of 82.0
The hydrocarbon decolourises bromine water.
Determine the empirical and molecular formulae of the hydrocarbon.
Suggest TWO possible structures for the hydrocarbon.
Name the type of reaction taking place when bromine water reacts with the
hydrocarbon. - Answer-C:H = 7.3 : 12.2
which is simplified to C:H = 3:5
Empirical formula = C3H5
Molecular formula = C6H10
2 structures of C6H10
Molecule with a triple bond
Cyclic compounds with one double bond
2024/2025
/Explain, in general terms, how a catalyst increases the rate of a reaction. - Answer-
provides a different route
With lower activation energy
/.Explain, in terms of collision theory, the effect of increasing the concentration of
hydrogen peroxide on the rate of reaction. - Answer-more moles in given volume
so successful collisions are more frequent
/.State why the student should use sodium hydroxide solution rather than water for the
final rinse of the burette. - Answer-use of water would dilute the NaOH
/.The total uncertainty when using the burette is ±0.15 cm3.
Using 23.95 as mean titre calculate % uncertainty - Answer-(0..95) x 100%
= 0.63
/.find the mass, in mg, of citric acid dissolved in 250 cm3 of the solution.
The relative molecular mass (Mr) of citric acid is 192.0.
Volume = 23.95 cm3 - Answer-moles NaOH = 23. x 0.0500
moles NaOH = 0.001198
moles acid in flask = 0.001198/3 titres x 10
moles acid in flask = 0.003992
mass acid = 0.003992 x 192.0 = 0.766 g
Mass acid = 766 (mg)
/.Calculate the percentage purity of this sample of citric acid. - Answer-(766/784 x 100 )
= 97.7
/.When ethanoic acid reacts with sodium hydroxide, the enthalpy change, ∆H, is -56.1
kJ mol-1
CH3COOH(aq) + NaOH(aq) ⟶CH3COONa(aq) + H2O(l)
Calculate the temperature rise when 25 cm3 of 2.0 mol dm-3 aqueous ethanoic acid
react with 25 cm3 of 2.0 mol dm-3 aqueous sodium hydroxide.
Assume that both solutions have the same initial temperature, have a density of 1.0 g
cm-3 and a specific heat capacity of 4.18 J K-1 g-1 - Answer-moles ( = 25/1000 x 2.0) =
0.050
, heat released = 0.050 x 56.1
heat released = 2.805 kJ
delta T = q / mc
delta T == 2805 50 x 4.18
delta T = 13.4 C
/.State the general formula of an alkane containing n carbon atoms. Deduce an
expression for the relative molecular mass (Mr) of an alkane in terms of n. - Answer-
General formula = CnH2n+2
Expression = 14.0n + 2.0 or 14n + 2
/.Explain why nonane has a higher boiling point than 2,4-dimethylheptane. - Answer-
nonane has stronger van der Waals' forces between molecules
Due to nonane molecules pack closer together
/.Nonane is often found in fuel for jet engines. Combustion in jet engines produces
pollutants including nitrogen monoxide (NO).
Explain how this nitrogen monoxide is formed - Answer-nitrogen and oxygen from air
react at high temperature
/.Give an equation for the complete combustion of nonane. - Answer-C9H20 + 14O2
9CO2 + 10H2O
/.Nonane can be cracked to form large quantities of propene.
Name the type of cracking used. - Answer-thermal cracking
/.A hydrocarbon contains 87.8% by mass of carbon and has a relative molecular mass
(Mr) of 82.0
The hydrocarbon decolourises bromine water.
Determine the empirical and molecular formulae of the hydrocarbon.
Suggest TWO possible structures for the hydrocarbon.
Name the type of reaction taking place when bromine water reacts with the
hydrocarbon. - Answer-C:H = 7.3 : 12.2
which is simplified to C:H = 3:5
Empirical formula = C3H5
Molecular formula = C6H10
2 structures of C6H10
Molecule with a triple bond
Cyclic compounds with one double bond
