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CAIE A-Level Chemistry Paper 3 Advanced Practical Skills

Practise laboratory measurement, observations, data presentation, analysis, conclusions and evaluation.

Syllabus
2028–2030
Course
Chemistry 9701
Level
AS

Exam points

  • manipulate apparatus safely and record measurements and qualitative observations at suitable precision
  • present raw data clearly, process it correctly and draw conclusions supported by the observations
  • evaluate reliability, identify limitations and propose specific experimental improvements

Covered syllabus points

P3.1—Successful collection of data and observationsP3.2—Measurement quality and concordancyP3.3—Decisions about measurements and observationsP3.4—Recording data and observationsP3.5—Calculations, reasoning and significant figuresP3.6—Data layout, tables and graphsP3.7—Interpreting data and drawing conclusionsP3.8—Errors, uncertainty, improvements and extensionsP3.9—Quantitative practical proceduresP3.10—Qualitative analysis notes and testsP3.11—Apparatus, materials, hazards and safety

Paper 3 Advanced Practical Skills question 1

[Maximum number: 1]

Aqueous bromine reacts with methanoic acid to form hydrogen bromide and carbon dioxide gas.

Br2(aq)+HCO2H(aq)→2HBr(aq)+CO2( g)\mathrm{Br}_{2}(\mathrm{aq})+\mathrm{HCO}_{2} \mathrm{H}(\mathrm{aq}) \rightarrow 2 \mathrm{HBr}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{~g})

The table shows the oxidation numbers of bromine and carbon in the species involved in this reaction.

Table for Question Paper 3 Advanced Practical Skills question 1 — CAIE A-Level Chemistry AS

Suggest one change you would observe, ignoring temperature changes, when bromine reacts with methanoic acid.

Paper 3 Advanced Practical Skills question 2

[Maximum number: 1]

The reaction between Na2 S2O3(aq)\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}(\mathrm{aq}) and HCl(aq) is monitored at constant temperature.

Na2 S2O3+2HCl→2NaCl+SO2+S+H2O\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}+2 \mathrm{HCl} \rightarrow 2 \mathrm{NaCl}+\mathrm{SO}_{2}+\mathrm{S}+\mathrm{H}_{2} \mathrm{O}

Fig. 4.1 shows how the concentration of HCl(aq) varies with time.

Fig. 4.1

Fig. 4.1

Explain why the rate of reaction cannot be monitored accurately by measuring the volume of SO2( g)\mathrm{SO}_{2}(\mathrm{~g}) produced in this reaction.

Paper 3 Advanced Practical Skills question 3

[Maximum number: 1]

Compound T is a white crystalline solid.
When a sample of compound T is mixed with aqueous sodium hydroxide and heated, a gas is produced which turns damp red litmus paper blue.

Further testing of a solution of compound T with aqueous barium chloride produces a dense white precipitate which does not dissolve when dilute hydrochloric acid is added to the mixture.

What is the identity of compound T ?

A

ammonium carbonate

B

ammonium sulfate

C

sodium carbonate

D

sodium sulfate

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