In a coffee cup calorimeter, 1.60 g of NH4NO3 is mixed with 75.0 g of water at an initial temperature of 25.008C. After dissolution of the salt, the final temperature of the calorimeter contents is 23.348C. Assuming the solution has a heat capacity of 4.18 J 8C21 g21 and assuming no heat loss to the calorimeter, calculate the enthalpy change for the dissolution of NH4NO3 in units of kJ/mol.

ΔH for the dissolution of is +26.0205 kJ/mol

Explanation:

The quantity of heat required to raise the temperature of a substance by one degree Celsius is called the specific heat capacity.

Q = Heat released by solution  = ?

C = heat capacity =

Initial temperature of water  = =

Final temperature of water  =  =

Change in temperature ,

Putting in the values, we get:

As heat released by water is equal to heat absorbed by dissolution of  

Enthalpy change for 0.02 moles of = 520.41 J

Enthalpy change for  1 mole of =

ΔH for the dissolution of is +26.0205 kJ/mol

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