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Date May 2017 Marks available 1 Reference code 17M.3.sl.TZ1.1
Level SL Paper 3 Time zone TZ1
Command term Calculate Question number 1 Adapted from N/A

Question

A class was determining the concentration of aqueous sodium hydroxide by titrating it with hydrochloric acid, whilst monitoring the pH of the solution. The sodium hydroxide solution was added into a glass beaker from a measuring cylinder and the hydrochloric acid added using a burette. One group of students accidentally used a temperature probe rather than a pH probe. Their results are given below.

Volume of aqueous NaOH = 25.0 ± 0.5 cm3

Concentration of HCl = 1.00 ± 0.01 mol dm−3

Calculate the percentage uncertainty of the volume of the aqueous sodium hydroxide.

[1]
a.

Suggest how the precision of this measurement could be improved.

[1]
b.

Markscheme

« 0.5 25.0 × 100 » = 2 «%»

[1 mark]

a.

pipette/pipet «rather than a measuring cylinder»

 

Accept “using a burette/buret”.

Accept “using a volumetric/measuring flask”.

Do not accept “use of a more precise measuring cylinder”.

[1 mark]

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Core » Topic 11: Measurement and data processing » 11.2 Graphical techniques
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Core » Topic 11: Measurement and data processing
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