A-LevelChemistryChemical energeticsOct/Nov 2025Paper 3 Q211 Marks
When hydrated sodium thiosulfate is dissolved in water the temperature of the liquid changes. You will carry out an experiment to determine the enthalpy change, ΔΗ, when one mole of hydrated sodium thiosulfate dissolves in water. FA 3 is hydrated sodium thiosulfate, Na2S2O3 5H2O. (a) Method • Support the cup in the 250 cm³ beaker. • Use the 50 cm³ measuring cylinder to transfer 30.0 cm³ of distilled water into the cup. • Measure the temperature of the water in the cup. Record this in the space for results. • Weigh the container with FA 3. Record the mass. • Tip all the FA 3 into the cup. • Stir the mixture until the minimum temperature is obtained. Record this temperature. • Weigh the container with any residual FA 3. Record the mass. • Calculate and record the mass of FA 3 added. • Calculate and record the temperature change. Results
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