Measuring Enthalpy Changes

Question 1

what does calorimetry allow you to measure?

Answer 1

the amount of energy transferred in a chemical reaction

Question 2

calorimetry - dissolving, displacement and neutralisation reactions

Answer 2

to measure the amount of energy transferred in these reactions you take the temperature of the reactants, mix them and measure the temperature of the solution at the end of the reaction
1. to investigate the enthalpy change of dissolving, displacement or neutralisation reactions you can do it by mixing the reactants in a polystyrene cup
2. to reduce the amount of energy lost to the surroundings put the polystyrene cup into a beaker of cotton wool to provide insulation and put a lid on the cup to reduce energy lost by evaporation

Question 3

calorimetry - combustion reactions

Answer 3

to measure the amount of energy transferred when a fuel is burnt, you can simply burn the fuel and use the flame to heat up some water - this method uses a metal container, usually made of copper because copper conducts heat so well
1. it is important to make as much heat as possible to go into heating up the water so to reduce draughts use a screen to act as a draught excluder (don’t do it next to a window)
2. put 50g of water in the copper can and record its temperature
3. weigh the spirit burner and lid
4. put the spirit burner underneath the can, and light the wick - then heat the water, stirring constantly, until the temperature reaches about 50 degrees C
5. put out the flame using the burner lid, and measure the final temperature of the water
6. weigh the spirit burner and lid again then use the measurements you’ve taken to calculate the enthalpy change