Calculating enthalpy changes

The for a reaction can be calculated using the following equation:

\(\Delta H=cm\Delta T\)

\(\Delta H\) is the enthalpy change (in kJ or kJ mol^-1)

c is the specific heat capacity of water.

It is a constant, 4.18 kJ kg^-1˚C^-1 and is found in the data book.

m is the mass of water (in kg) (Remember that 100 cm³ = 0.1 kg)

\(\Delta T\) is the change in temperature (˚C)

Example

Question

A solution was made by dissolving a spatula of potassium nitrate into 50 cm³ of water. The temperature changed from 20.4˚C to 18.7˚C. Calculate the enthalpy change for this reaction.

Enthalpy of combustion

Enthalpy

Revise: Chemical energyCalculating enthalpy changes