, Oxford Cambridge and RSA
Monday 19 June 2023 – Afternoon
A Level Chemistry B (Salters)
H433/02 Scientific literacy in chemistry
Time allowed: 2 hours 15 minutes
You must have:
* 9 9 0 1 5 5 4 6 6 5 *
• a clean copy of the Advance Notice Article (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 2 *
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 100.
• 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 24 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2023 [601/5371/4] OCR is an exempt Charity
DC (ST/JG) 318015/4 Turn over
, 2
1 The element bromine is extracted from seawater.
Bromide ions are present in seawater in very low concentrations compared with chloride ions.
(a) (i) Excess chlorine is added to acidified seawater, forming aqueous bromine.
Write an ionic equation for the reaction of chlorine with bromide ions and explain how it
shows that chlorine is more reactive than bromine.
Equation:
Explanation: ......................................................................................................................
...........................................................................................................................................
[2]
(ii) Air is blown through the mixture to remove the bromine as a vapour.
Sulfur dioxide is then added, and the mixture is dissolved in water.
Bromine reacts to form concentrated HBr.
Br2(aq) + SO2(aq) + 2H2O(l) 2HBr(aq) + H2SO4(aq)
What is the oxidising agent in this reaction?
Explain your answer using oxidation states.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [2]
(iii) Concentrated Br2 is made from the concentrated HBr by displacement using chlorine.
Complete the table to give the properties of chlorine, bromine and iodine.
Colour at room Physical state at room
Halogen
temperature temperature
chlorine
bromine
iodine
[2]
© OCR 2023
, 3
(b) Some of the hazards of transporting bromine are similar to those of transporting chlorine.
Suggest two hazards of transporting bromine in a road tanker.
Hazard 1 ...................................................................................................................................
...................................................................................................................................................
Hazard 2 ...................................................................................................................................
...................................................................................................................................................
[2]
(c) Some students add aqueous silver nitrate to a sample of seawater.
They expect to see a cream precipitate of silver bromide but the precipitate is pure white.
(i) Write an ionic equation for the reaction of silver ions with bromide ions.
Show state symbols.
[2]
(ii) Suggest why the students do not get the result they expect.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [2]
(d) The students titrate 25.0 cm3 of a solution of bromine with sodium thiosulfate in the presence
of excess iodide ions.
Br2 + 2I– 2Br– + I2
I2 + 2S2O32– S4O62– + 2I–
They find that 24.65 cm3 of 0.380 mol dm–3 sodium thiosulfate is required to reach the end
point.
Calculate the concentration of Br2 in mol dm–3.
concentration = .......................................... mol dm–3 [2]
© OCR 2023 Turn over
Monday 19 June 2023 – Afternoon
A Level Chemistry B (Salters)
H433/02 Scientific literacy in chemistry
Time allowed: 2 hours 15 minutes
You must have:
* 9 9 0 1 5 5 4 6 6 5 *
• a clean copy of the Advance Notice Article (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 2 *
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 100.
• 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 24 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2023 [601/5371/4] OCR is an exempt Charity
DC (ST/JG) 318015/4 Turn over
, 2
1 The element bromine is extracted from seawater.
Bromide ions are present in seawater in very low concentrations compared with chloride ions.
(a) (i) Excess chlorine is added to acidified seawater, forming aqueous bromine.
Write an ionic equation for the reaction of chlorine with bromide ions and explain how it
shows that chlorine is more reactive than bromine.
Equation:
Explanation: ......................................................................................................................
...........................................................................................................................................
[2]
(ii) Air is blown through the mixture to remove the bromine as a vapour.
Sulfur dioxide is then added, and the mixture is dissolved in water.
Bromine reacts to form concentrated HBr.
Br2(aq) + SO2(aq) + 2H2O(l) 2HBr(aq) + H2SO4(aq)
What is the oxidising agent in this reaction?
Explain your answer using oxidation states.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [2]
(iii) Concentrated Br2 is made from the concentrated HBr by displacement using chlorine.
Complete the table to give the properties of chlorine, bromine and iodine.
Colour at room Physical state at room
Halogen
temperature temperature
chlorine
bromine
iodine
[2]
© OCR 2023
, 3
(b) Some of the hazards of transporting bromine are similar to those of transporting chlorine.
Suggest two hazards of transporting bromine in a road tanker.
Hazard 1 ...................................................................................................................................
...................................................................................................................................................
Hazard 2 ...................................................................................................................................
...................................................................................................................................................
[2]
(c) Some students add aqueous silver nitrate to a sample of seawater.
They expect to see a cream precipitate of silver bromide but the precipitate is pure white.
(i) Write an ionic equation for the reaction of silver ions with bromide ions.
Show state symbols.
[2]
(ii) Suggest why the students do not get the result they expect.
...........................................................................................................................................
...........................................................................................................................................
...........................................................................................................................................
...................................................................................................................................... [2]
(d) The students titrate 25.0 cm3 of a solution of bromine with sodium thiosulfate in the presence
of excess iodide ions.
Br2 + 2I– 2Br– + I2
I2 + 2S2O32– S4O62– + 2I–
They find that 24.65 cm3 of 0.380 mol dm–3 sodium thiosulfate is required to reach the end
point.
Calculate the concentration of Br2 in mol dm–3.
concentration = .......................................... mol dm–3 [2]
© OCR 2023 Turn over
