Using the provided materials, determine the enthalpy of (heat of) solution, in kJ/mol, for the three — Calorimetry and Enthalpy of Solution Chemistry Question
Problem Context
Using the provided materials, determine the enthalpy of (heat of) solution, in kJ/mol, for the three unknown solids.
Give a brief description of your experimental plan.
Model Answer
Procedures will vary, but should follow the basic steps of:
1. Measure a volume, or weigh an amount, of water.
2. Place water in calorimetry cup. Some students may have weighed calorimetry apparatus before and after addition of water.
3. Take temperature of water.
4. Weigh out an amount of unknown solid.
5. Add solid to water in calorimetry cup.
6. Some form of stirring or swirling of the cup.
7. Record new temperature.
Record your data/observations.
Model Answer
Students should create a data table, or clearly show their collected data. Students should provide more than one trial for each unknown.
Show all calculations.
Model Answer
Sample Calculations:
Unknown 1 ∆Hsol = +13.9 kJ/mol. 60.06 g/mol. +231 J/g
qwater = mc∆T. q = (25.15g)(4.18 J/g* C)(17.3 C - 22.4 C) = -536.15 J
qwater = -qhydration qhydration = +536.15 J
∆Hsol = 536.15 J / 2.06 g = +260.3 J/g or for unknown 1 +15.63 kJ/mol (Endothermic)
Unknown 2 ∆Hsol = -26.7 kJ/mol. 105.99 g/mol. 252 J/g
qwater = mc∆T. q = (27.59g)(4.18 J/g* C)(27.6 C - 22.5 C) = +588.16 J
qwater = -qhydration qhydration = -588.16 J
∆Hsol = -588.16 J / 2.18 g = -269.8 J/g or for unknown 2 -28.60 kJ/mol (Exothermic)
Unknown 3 ∆Hsol = -17.3 kJ/mol 82.03 g/mol -211 J/g
qwater = mc∆T. q = (22.67g)(4.18 J/g* C)(27.0 C - 22.2 C) = +454.85 J
qwater = -qhydration qhydration = -454.85 J
∆Hsol = -454.85 J / 2.26 g = -201.3 J/g or for unknown 3 -16.51 kJ/mol (Exothermic)
The enthalpy of solution for unknown 1 is __________ kJ/mol.
The enthalpy of solution for unknown 2 is __________ kJ/mol.
The enthalpy of solution for unknown 3 is __________ kJ/mol.