When a solid dissolves in water, heat may be evolved or absorbed. The heat of di

Question

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 10.14 g of CsBr(s) are dissolved in 100.00 g of water, the temperature of the solution drops from 24.42 to 21.05 °C.

The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.63 J/°C.

Based on the student's observation, calculate the enthalpy of dissolution of CsBr(s) in kJ/mol.

Assume the specific heat of the solution is equal to the specific heat of water. 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 10.14 g of CsBr(s) are dissolved in 100.00 g of water, the temperature of the solution drops from 24.42 to 21.05 °C.

The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.63 J/°C.

Based on the student's observation, calculate the enthalpy of dissolution of CsBr(s) in kJ/mol.

Assume the specific heat of the solution is equal to the specific heat of water.

Explanation / Answer

(4.18 J/g·°C) x (100.00 g) x (24.42 - 21.05)°C = 1410.008 J lost by the water

Supposing the calorimeter to be at the same temperatures as the water:
(1.63 J/°C) x (24.42 - 21.05)°C = 5.49 J lost by the calorimeter

1410.008 J + 5.49 J = 1415.49 J total lost by the combined apparatus, and gained by the solute

(1.41549 kJ) / ((10.14 g of CsBr) / (212.81 g CsBr/mol)) = +29.70 kJ/mol

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