Skip to content
MathsGenie logo
Open app

Course home

  1. A Level
  3. Chemistry AQA
  5. Question bank

Energetics

EasyMedium
1234567891011121314151617181920212223
Question 20

A student performs a calorimetry experiment to determine the enthalpy of solution of anhydrous calcium chloride, CaCl2\text{CaCl}_2CaCl2​.

The student uses the following method:

  • Measure 75.0 cm375.0\text{ cm}^375.0 cm3 of distilled water into a polystyrene cup.
  • Record the initial temperature of the water.
  • Add 5.55 g5.55\text{ g}5.55 g of anhydrous CaCl2\text{CaCl}_2CaCl2​ and stir.
  • Record the highest temperature reached.

Results:

  • Initial temperature: 20.2 ∘C20.2\ ^\circ\text{C}20.2 ∘C
  • Highest temperature: 32.7 ∘C32.7\ ^\circ\text{C}32.7 ∘C

Constants & Assumptions:

  • Specific heat capacity of the solution: c=4.18 J K−1 g−1c = 4.18\text{ J K}^{-1}\text{ g}^{-1}c=4.18 J K−1 g−1
  • Density of the solution: 1.00 g cm−31.00\text{ g cm}^{-3}1.00 g cm−3
  • Molar mass of CaCl2\text{CaCl}_2CaCl2​: 111.0 g mol−1111.0\text{ g mol}^{-1}111.0 g mol−1
a.

Calculate the enthalpy of solution, in kJ mol−1\text{kJ mol}^{-1}kJ mol−1, for anhydrous calcium chloride in this experiment. Give your answer to 3 significant figures.

[4]
b.

The uncertainty in each temperature reading from the thermometer is ±0.15 ∘C\pm0.15\ ^\circ\text{C}±0.15 ∘C. Calculate the percentage uncertainty in the temperature change for this experiment.

[2]

Energetics Questions

  1. A Level
  2. /Chemistry
  3. /Energetics