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In the laboratory a general chemistry student finds that when 2.91 g CoSO4(s) is dissolved in 114.50 g water, the temperature of the solution increases from 25.70 to 28.83 °c. the heat capacity of the calorimeter was determined in a separate experiment to be 1.73 J/°C. Based on the student's observation, calculate the dissolution enthalpy of CoSO4(s) in kj/mol.
Accepted Answer
The dissolution enthalpy of CoSO4(s) can be calculated using the following steps:
1. Calculate the heat absorbed by the solution:
- ΔT = 28.83 °C - 25.70 °C = 3.13 °C
- q_solution = m_solution
C_solution
ΔT
- Assuming the specific heat capacity of water is 4.184 J/g°C, the heat absorbed by the solution is:
q_solution = (114.50 g + 2.91 g)
4.184 J/g°C
3.13 °C = 1535.6 J
2. Calculate the heat absorbed by the calorimeter:
- q_calorimeter = C_calorimeter
ΔT
- q_calorimeter = 1.73 J/°C
3.13 °C = 5.42 J
3. Calculate the total heat absorbed:
- q_total = q_solution + q_calorimeter = 1535.6 J + 5.42 J = 1541.0 J
4. Calculate the moles of CoSO4:
- Molar mass of CoSO4 = 155.0 g/mol
- Moles of CoSO4 = 2.91 g / 155.0 g/mol = 0.0188 mol
5. Calculate the dissolution enthalpy:
- ΔH_dissolution = q_total / moles of CoSO4
- ΔH_dissolution = 1541.0 J / 0.0188 mol = 81914.9 J/mol = 81.9 kJ/mol
Therefore, the dissolution enthalpy of CoSO4(s) is 81.9 kJ/mol.
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