34.6 determine enthalpy change of neutralisation

A. Sketch setup
- Expanded polystyrene cup : good heat insulator , reduce heat loss to surroundings
- cotton and air in between the cup and beaker : reduce heat loss to surroundings by conduction

B. Assumption
- Assume the specific heat capacity and density of reaction mixture (salt solution) is the same as that of water

C. Calculations
0. Mass of water = density x vol
1. Energy released = mc T bn bv
2. No. of acid & alkali used , no of water formed (Pay attention to limited reagent question)
3. Standard enthalpy change of neutralization = - E / no. of water

D. Features
Should not be more negative than -57.3 kJ mol-1

E. Sources of error
1. Heat lost to surroundings
2. Heat capacity of thermometer and expanded polystyrene cups are not taken into account
3. The density and specific heat capacity of reaction mixture is not the same as that of water
4. The experiment is not carried out under standard conditions

F. Improvement
1. Use vacuum flask to reduce heat lost to surroundings
2. Take heat capacity of thermometer and expanded polystyrene cups into account
3. Should use the density and specific heat capacity of reaction mixture.