Hydrated copper(II) sulfate, CuSO4•5H2O, can lose its water of crystallisation to form anhydrous copper(II) sulfate. The enthalpy change for the dehydration of hydrated copper(II) sulfate is shown in the equation. CuSO4.5H2O(s) → CuSO4(s) + 5H2O(l) You will carry out experiments to determine the enthalpy changes for the solution of hydrated and anhydrous copper(II) sulfate and then use Hess's law to determine the enthalpy change of dehydration. FA 4 is hydrated copper(II) sulfate, CuSO4•5H2O. FA 5 is anhydrous copper(II) sulfate, CuSO4.

1. (a)Determination of the enthalpy change of solution of hydrated copper(II) sulfate. Method • Weigh the container with FA 4. Record the mass. • Support the cup in the 250 cm³ beaker. • Use the measuring cylinder to transfer 25.0 cm³ of distilled water into the cup. • Measure and record the temperature of the water. • Tip all the FA 4 into the water and stir until the solid dissolves. • Measure and record the lowest temperature reached. • Rinse and dry the cup ready for the next experiment. • Weigh the container with any residual FA 4. Record the mass. • Calculate and record the change in temperature. • Calculate and record the mass of FA 4 used. Results[2]
2. (b)(i)Calculate the energy change during this reaction. energy change = ................................... J[1]
3. (b)(ii)Calculate the amount, in mol, of hydrated copper(II) sulfate, FA 4, used in the experiment. Show your working. amount of CuSO4•5H2O = ................................... mol[1]
4. (b)(iii)Calculate the enthalpy change, in kJ mol-¹, when 1.00 mol of hydrated copper(II) sulfate dissolves in water. This is the enthalpy of solution. enthalpy change of solution = ................................... kJ mol-1 sign value[1]
5. (c)Determination of the enthalpy change of solution of anhydrous copper(II) sulfate. Method • Weigh the container with FA 5. Record the mass. • Support the cup in the 250 cm³ beaker. • Use the measuring cylinder to transfer 25.0 cm³ of distilled water into the cup. • Measure and record the temperature of the water. • Tip all the FA 5 into the water and stir until the solid dissolves. • Measure and record the highest temperature reached. • Weigh the container with any residual FA 5. Record the mass. • Calculate and record the change in temperature. • Calculate and record the mass of FA 5 used. Results[1]
6. (d)(i)Calculate the enthalpy change, in kJ mol-¹, for the enthalpy change of solution of anhydrous copper(II) sulfate. enthalpy change = ................................... kJ mol-1 sign value[2]
7. (d)(ii)Use the enthalpy changes calculated in (b)(iii) and (d)(i) to calculate the enthalpy change of dehydration of hydrated copper(II) sulfate. CuSO4.5H2O(s) → CuSO4(s) + 5H2O(l) Show clearly how you obtained your answer. enthalpy change = ................................... kJ mol-1 sign value[1]
8. (e)In the experiments in (a) and (c) you used the same method to determine the enthalpy change of solution of two solids. Tick the box to indicate which statement is correct. Ignore the effect of differences in mass used. The percentage error in (b)(iii) is less than the percentage error in (d)(i). [ ] The percentage errors in (b)(iii) and (d)(i) are equal. [ ] The percentage error in (b)(iii) is greater than the percentage error in (d)(i). [ ] Explain your choice.[1]