SUMMER 2026
PREDICTED PAPER
A Level Chemistry B (Salters)
H433/02 Scientific literacy in chemistry
OCR
Time allowed: 2 hours 15 minutes
You must have:
• 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
a ruler (cm/mm)
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 25 pages.
ADVICE
• Read each question carefully before you start your answer.
Turn over
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, 2
1 A buffer solution is prepared by mixing a weak acid with its conjugate base. Such
a solution resists changes in pH when small amounts of acid or alkali are added.
(a) A student prepares a buffer solution by mixing 300 cm³ of 0.150 mol dm⁻³ ethanoic
acid with 200 cm³ of 0.200 mol dm⁻³ sodium ethanoate solution. The Ka of ethanoic
acid is 1.8 × 10⁻⁵ mol dm⁻³.
(i) Calculate the concentration of ethanoic acid and sodium ethanoate after mixing. Show
all working clearly.
concentration of ethanoic acid..........................
concentration of sodium ethanoate................... [2]
(ii) Using your answers from (i), calculate the pH of the buffer solution.
pH of the buffer solution................... [2]
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, 3
(iii) A small amount of dilute hydrochloric acid is added to the buffer solution. Using an
equation, explain how the buffer resists a decrease in pH.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
................................................................................................................................... [2]
(iv) A small amount of dilute hydrochloric acid is added to the buffer solution. Using an
equation, explain how the buffer resists a decrease in pH.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
................................................................................................................................... [1]
(b) The table shows how the value of Kw changes with temperature.
Temperature (°C) Kw (mol² dm⁻⁶)
10 2.93 × 10⁻¹⁵
25 1.00 × 10⁻¹⁴
40 2.92 × 10⁻¹⁴
60 9.55 × 10⁻¹⁴
(i) Define the ionic product of water, Kw, and write the expression for it.
...................................................................................................................................
...................................................................................................................................
................................................................................................................................... [1]
for more: tyrionpapers.com
PREDICTED PAPER
A Level Chemistry B (Salters)
H433/02 Scientific literacy in chemistry
OCR
Time allowed: 2 hours 15 minutes
You must have:
• 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
a ruler (cm/mm)
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 25 pages.
ADVICE
• Read each question carefully before you start your answer.
Turn over
for more: tyrionpapers.com
, 2
1 A buffer solution is prepared by mixing a weak acid with its conjugate base. Such
a solution resists changes in pH when small amounts of acid or alkali are added.
(a) A student prepares a buffer solution by mixing 300 cm³ of 0.150 mol dm⁻³ ethanoic
acid with 200 cm³ of 0.200 mol dm⁻³ sodium ethanoate solution. The Ka of ethanoic
acid is 1.8 × 10⁻⁵ mol dm⁻³.
(i) Calculate the concentration of ethanoic acid and sodium ethanoate after mixing. Show
all working clearly.
concentration of ethanoic acid..........................
concentration of sodium ethanoate................... [2]
(ii) Using your answers from (i), calculate the pH of the buffer solution.
pH of the buffer solution................... [2]
for more: tyrionpapers.com
, 3
(iii) A small amount of dilute hydrochloric acid is added to the buffer solution. Using an
equation, explain how the buffer resists a decrease in pH.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
................................................................................................................................... [2]
(iv) A small amount of dilute hydrochloric acid is added to the buffer solution. Using an
equation, explain how the buffer resists a decrease in pH.
...................................................................................................................................
...................................................................................................................................
...................................................................................................................................
................................................................................................................................... [1]
(b) The table shows how the value of Kw changes with temperature.
Temperature (°C) Kw (mol² dm⁻⁶)
10 2.93 × 10⁻¹⁵
25 1.00 × 10⁻¹⁴
40 2.92 × 10⁻¹⁴
60 9.55 × 10⁻¹⁴
(i) Define the ionic product of water, Kw, and write the expression for it.
...................................................................................................................................
...................................................................................................................................
................................................................................................................................... [1]
for more: tyrionpapers.com
