Edexcel IAL Chemistry A2 Measurement Uncertainty

Edexcel IAL Chemistry A2 Measurement Uncertainty
Pearson Edexcel International Advanced Subsidiary/Advanced Level in Chemistry, Issue 1, September 2017Chemistry XCH11/YCH11

Practise Edexcel IAL Chemistry measurement uncertainty through burette, thermometer and balance readings, percentage uncertainty and ways to reduce it.

How this is tested

  • Double reading uncertainties for temperature changes or titres before calculating percentage uncertainty.
  • Work backwards from percentage uncertainty to a titre, or state balance ranges from two mass readings.
  • Explain how increasing the measured change reduces percentage uncertainty without changing apparatus.

Question 1(a)

[Maximum number: 1]

A student measures the enthalpy change of combustion, ΔcH\Delta_{\mathrm{c}} H, of methanol, CH3OH\mathrm{CH}_{3} \mathrm{OH}, using the apparatus shown.

Figure for Question 1(a) — Edexcel A-Level Chemistry A2

After burning 0.20 g of methanol, the temperature of the water increases by 16.0∘C16.0^{\circ} \mathrm{C}.

The measurement uncertainty in the thermometer used in the experiment is 0.5∘C0.5^{\circ} \mathrm{C} for each reading.

What is the percentage uncertainty in the temperature change of 16.0∘C16.0^{\circ} \mathrm{C} ?
□ A1.6\%
□ B3.1\%
□ C 6.3\%
□ D 12.5%