RP2 - Measurement of Enthalpy change

Question 1

What is this reaction also referred to?

Answer 1

Enthalpy change of neutralisation/ Neutralisation Titration (with sulphuric acid and NaOH

Question 2

Describe the method for this reaction?

Answer 2

1. weight out 4.00g of anhydrous copper sulphate in a dry stoppered weighing bottle
2. construct a suitable table of results to record your temperature in
3. using a measuring cylinder, place 25cm3 of deionised water into a polystyrene cup and record it’s initial temperature change.
4. Start the timer and record and continue to record the temperature each minute for 3 minutes.
5. At the fourth minute add the anhydrous copper sulphate to the water in the polystyrene cup, but do not record the temperature. At the fifth minute continue the temperature readings, until you reach 15 minutes, Stir the solution as this is done.
6. Plot a graph of temperature on the y-axis against time. Draw two separate lines of best fit , one which joins the points before addition, one which joins the points after addition. Extrapolate both lines to the fourth minute.
7. Use your graph to determine the temperature change at the fourth minute, which theoretically should have occurred after the addition of the Anhydrous copper sulphate.

Question 3

Draw two diagrams to show this experiment set up.

Question 4

What are some common errors that occur during this investigation?

Answer 4

• Heat loss to surroundings
• The method assumes that all solutions have the specific heat capacity of water
• Any heat absorbed by the apparatus is ignored
• reaction or dissolving may be incomplete or slow
• density of solution is taken to be the same as water
• Some of the water could have evaporated
• Room temperature could have changed
• Incomplete combustion if using a fuel

Question 5

How would we improve the accuracy

Answer 5

• An electronic temperature sensor and data logging software could be used to plot graph accurately
• A flame colorimeter could be used to improve accuracy:
  -Spiral chimney is made up of copper
  -Flame is enclosed
  -Fuel burns in pure oxygen rather than air

Question 6

DONE!!