When a solid dissolves in water, heat may be evolved or absorbed. the heat of dissolution (dissolving) can be determined using a coffee cup calorimeter. in the laboratory a general chemistry student finds that when 5.15 g of nh4br(s) are dissolved in 105.00 g of water, the temperature of the solution drops from 23.82 to 21.63 °c. the heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.76 j/°c. based on the student's observation, calculate the enthalpy of dissolution of nh4br(s) in kj/mol.

Answer : The enthalpy change of dissolution of is 18.4 kJ/mole

Explanation :

Heat released by the reaction = Heat absorbed by the calorimeter + Heat absorbed by the water

where,

q = heat released by the reaction

= heat absorbed by the calorimeter

= heat absorbed by the water

= specific heat of calorimeter =

= specific heat of water =

= mass of water = 105.00 g

= change in temperature =

Now put all the given values in the above formula, we get:

Now we have to calculate the enthalpy change of dissolution of

where,

= enthalpy change = ?

q = heat released = 0.966 kJ

m = mass of = 5.15 g

Molar mass of = 97.94 g/mol

Therefore, the enthalpy change of dissolution of is 18.4 kJ/mole