Required practical 2 - Measuring enthalpy changes

Outline the method for this practical:

This reaction in particular is exothermic.'

Anhydrous copper sulfate + aq → Copper sulfate solution

• Weigh anhydrous copper sulfate amount 4 grams

• Place thermometer in polystyrene cup and record the temperature of 25cm cubed of deionised water for every 30 seconds

• start the timer when adding the anhydrous copper sulfate (stir) and record temperature every 30 seconds for 4 minutes

• Plot a graph with the temperature on y axis and time of x-axis. Draw two separate best fit lines, and one that joins the points after addition, extrapolate the lines to the fourth minute.

• Use the graph to determine the temperature change at the fourth minute, which is the theoretical temperature rise as soon as addition of solid

Errors:

• There is some heat transfer to or from the surrounding

• The method assumes all solutions have the heat capacity of water

• Some of the water could be evaporated

To improve accuracy:

• Polystryene cup (if not stated in the question) should be used to reduce heat loss to the surrounding

• A flame calorimeter could be used to improve accuracy

  • Spiral chimney of copper, good conductor of heat

  • Flame is enclosed

  • Fuel burns in pure oxygen instead of air

How does a flame calorimetry look like?