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Chemistry ■ ■


Advanced Subsidiary
PAPER 2: Core Organic and Physical Chemistry

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•
Use black ink or ball‑point pen.
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Fill in the boxes at the top of this page with your name,
centre number and candidate number.


• Answer the questions in the spaces provided
– there may be more space than you need.
Information
The total mark for this paper is 80.
The marks for each question are shown in brackets
– use this as a guide as to how much time to spend on each question.
For the question marked with an asterisk (*), marks will be awarded for your ability
to structure your answer logically, showing the points that you make are related or
follow on from each other where appropriate.
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Show all your working in calculations and include units where appropriate.
Check your answers if you have time at the end.
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P76894A
©2024 Pearson Education Ltd.
F:1/1/1/1/

, Answer ALL questions.

Some questions must be answered with a cross in a box . If you change your mind about an
answer, put a line through the box and then mark your new answer with a cross .

1 The relative molecular mass of a solid dicarboxylic acid, HOOC(CH2)nCOOH, can be
found using a titration. The acid, which can be represented as H2A, was dissolved in
deionised water and the solution made up to 250 cm3.
(a) Which piece of apparatus should be used for making a solution with a volume of
exactly 250 cm3 ?
(1)
A burette
B measuring cylinder

C pipette

D volumetric flask


(b) A solution of 0.100 mol dm–3 sodium hydroxide solution was added to a burette.
A rough titration was carried out on a 25.0 cm3 portion of the acid solution.

(i) The diagram shows the burette before the rough titration.

What is the initial burette reading for this titration?
(1)

2.0




3.0


A 2.40 cm3

B 2.45 cm3
C 3.55 cm3

D 3.60 cm3

, (ii) The final burette reading for the rough titration was 26.50 cm3.

Calculate the volume of sodium hydroxide solution added in the
rough titration, using your answer to (b)(i).
(1)




(iii) Describe how you would use the rough titration value when carrying out the
accurate titrations.
(1)

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. .. .. ... .. .. ... .. ... .. .. ... .. .. ... .. .. ... .. ... .. .. ... .. .. ... .. .. ... .. .. .. .. ... .. .. ... .. ... .. .. ... .. .. ... .. .. ... .. ... .. .. ... .. .. .. ... .. .. .. ... .. .. ... .. ... .. .. ... .. .. ... .. .. ... .. ... .. .. ... .. .. ... .. .. ... .. .. .. .. ... .. .. ... .. ... .. .. ... .. .. ... .. .. ... .. ... .. . . . ......................

, (c) 25.0 cm3 portions of the acid solution were titrated with
0.100 mol dm–3 sodium hydroxide solution.

The equation for the reaction is shown.

H2A(aq) + 2NaOH(aq)  Na2A(aq) + 2H2O(l)

The acid solution was pipetted into a conical flask and titrated.
The accurate titrations were carried out three times.
The following results were recorded for the accurate titrations.


Titration number 1 2 3

Burette reading (final) / cm3 47.80 24.35 47.60

Burette reading (initial) / cm3 24.50 1.00 24.35

Volume of NaOH used / cm3 23.30 23.35 23.25


(i) Calculate the mean titre for these accurate titrations.
(1)




(ii) Calculate the number of moles of sodium hydroxide in the mean titre.
(1)