, Oxford Cambridge and RSA
Friday 23 June 2023 – Morning
A Level Chemistry B (Salters)
H433/03 Practical skills in chemistry
Time allowed: 1 hour 30 minutes
You must have:
* 9 9 0 2 0 7 0 6 0 4 *
• the Practical Insert (inside this document)
• the Data Sheet for Chemistry B
You can use:
• a scientific or graphical calculator
• an HB pencil
* H 4 3 3 0 3 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 60.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 16 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2023 [601/5371/4] OCR is an exempt Charity
DC (RW/CB) 319189/3 Turn over
, 2
1 Ozone, O3, is a serious pollutant when present in the troposphere.
(a) Give one polluting effect of ozone in the troposphere.
...................................................................................................................................................
.............................................................................................................................................. [1]
(b) Tropospheric ozone is produced by the reactions of nitrogen oxides, NOx, and hydrocarbons.
These, together with carbon monoxide, CO, are pollutants produced by motor vehicles.
Catalytic converters in vehicle exhausts catalyse the reaction in Equation 1.1 and also the
oxidation of hydrocarbons to carbon dioxide and water.
2NO(g) + 2CO(g) N2(g) + 2CO2(g) Equation 1.1
(i) The bar chart below shows the reduction in the various pollutant levels when a suitable
catalytic converter is fitted.
Calculate the percentage reduction in NOx levels when a catalytic converter is fitted.
Give your answer to 2 significant figures.
9000
8000
7000
6000
parts per million 5000
(by volume) Without catalytic converter
4000
With catalytic converter
3000
2000
1000
0
C xH y NOx CO
pollutant
percentage reduction ..................................................... % [2]
© OCR 2023
, 3
(ii) A student says that the reactions in a catalytic converter decrease car pollution to zero.
Comment on this statement.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [3]
(iii) The diagram below represents an energy profile for the catalysed reaction in
Equation 1.1.
enthalpy
reactants
products
progress of reaction
On the diagram:
• Indicate the activation enthalpy of the catalysed reaction.
• Draw a progress curve for the uncatalysed reaction.
[1]
© OCR 2023 Turn over
Friday 23 June 2023 – Morning
A Level Chemistry B (Salters)
H433/03 Practical skills in chemistry
Time allowed: 1 hour 30 minutes
You must have:
* 9 9 0 2 0 7 0 6 0 4 *
• the Practical Insert (inside this document)
• the Data Sheet for Chemistry B
You can use:
• a scientific or graphical calculator
• an HB pencil
* H 4 3 3 0 3 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined pages at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answer should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 60.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 16 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2023 [601/5371/4] OCR is an exempt Charity
DC (RW/CB) 319189/3 Turn over
, 2
1 Ozone, O3, is a serious pollutant when present in the troposphere.
(a) Give one polluting effect of ozone in the troposphere.
...................................................................................................................................................
.............................................................................................................................................. [1]
(b) Tropospheric ozone is produced by the reactions of nitrogen oxides, NOx, and hydrocarbons.
These, together with carbon monoxide, CO, are pollutants produced by motor vehicles.
Catalytic converters in vehicle exhausts catalyse the reaction in Equation 1.1 and also the
oxidation of hydrocarbons to carbon dioxide and water.
2NO(g) + 2CO(g) N2(g) + 2CO2(g) Equation 1.1
(i) The bar chart below shows the reduction in the various pollutant levels when a suitable
catalytic converter is fitted.
Calculate the percentage reduction in NOx levels when a catalytic converter is fitted.
Give your answer to 2 significant figures.
9000
8000
7000
6000
parts per million 5000
(by volume) Without catalytic converter
4000
With catalytic converter
3000
2000
1000
0
C xH y NOx CO
pollutant
percentage reduction ..................................................... % [2]
© OCR 2023
, 3
(ii) A student says that the reactions in a catalytic converter decrease car pollution to zero.
Comment on this statement.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [3]
(iii) The diagram below represents an energy profile for the catalysed reaction in
Equation 1.1.
enthalpy
reactants
products
progress of reaction
On the diagram:
• Indicate the activation enthalpy of the catalysed reaction.
• Draw a progress curve for the uncatalysed reaction.
[1]
© OCR 2023 Turn over
