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 24.22 g of BaBr2 (s) are dissolved in 118.20 g of water, the temperature of the solution increases from 24.85 to 28.18 °C. The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.84 J/°C. Based on the student's observation, calculate the enthalpy of dissolution of BaBr2 (s) in kJ/mol. Assume the specific heat of the solution is equal to the specific heat of water.

Question

Madeleine

Chemistry

14 April, 12:08

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 24.22 g of BaBr2 (s) are dissolved in 118.20 g of water, the temperature of the solution increases from 24.85 to 28.18 °C. The heat capacity of the calorimeter (sometimes referred to as the calorimeter constant) was determined in a separate experiment to be 1.84 J/°C. Based on the student's observation, calculate the enthalpy of dissolution of BaBr2 (s) in kJ/mol. Assume the specific heat of the solution is equal to the specific heat of water.

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Sariah Levine · Answer 1

The enthalpy of dissolution of BaBr2 (s) is - 8,94 kJ/mol

Explanation:

In a dissolution process, the heat is released, so it must be negative (-)

The same to ΔH.

Q = m. C. ΔT

Q = 118,2 g. 1,84 J/g°C. (Tfinal - Tinitial)

Q = 118,2 g. 1,84 J/g°C. (28,18°C - 24,85°C)

Q = 118,2 g. 1,84 J/g°C. 3,33°C

Q = 724,2 J

724,2 J / 1000 = 0,7242 kJ

We dissolved 24,22g of BaBr2

Molar mass BaBr2: 297,13 g/m

We dissolved 24,22 g / 297,13 g/m = 0,081 moles

ΔH = kJ/mol

ΔH = - 0,7242 kJ / 0,081 mol

ΔH = - 8,94kJ/mol