Chemical reactions are invariably associated with the transfter of energy either in the form of heat or light. In the laboratory, heat changes in physical and chemical processes are measured with an instrument called calorimeter. Heat change in the process is calculated as
`{:(q = ms DeltaT,,s ="Specific heat"),(=cDeltaT,,c ="Heat capacity"):}`
Heat of reaction at constant volume is measured using bomb calorimeter.
`q_(V) = DeltaU =` Internal energy change
Heat of reaction at constant pressure is measured using simple or water calorimeter.
`q_(p) = DeltaH`
`q_(p) = q_(V) +P DeltaV`
`DeltaH = DeltaU +DeltanRT`
The enthalpy of fusion of ice is `6.02 kJ mol^(-1)`. The heat capacity of water is `4.18 J g^(-1)C^(-1)`. What is the smallest number of ice cubes at `0^(@)C`, each containing one molw of water, the are needed to cool `500g` of liquid water from `20^(@)C to 0^(@)C`?

Explanation

`C _(P) =r + C _(V) = (R//M) + C _(V) = (8.3//4xx 10 ^(-3)) + 3129 = 5204 Jkg ^(-1) K ^(-1)`