Before you start
Measure the enthalpy of ammonium nitrate dissolution
Tare a weighing boat, weigh 2.50 g of ammonium nitrate, add it to 100.00 mL of water, mix, and record the cooling caused by endothermic dissolution.
- Time
- about 15 minutes
- Level
- Intermediate
- Steps
- 3
What you are doing
Use a tared balance and coffee-cup calorimeter to connect measured solid mass, temperature change, and molar enthalpy.
Procedure
- Tare, weigh, and record the solidPlace the empty weighing boat on the balance, tare it, transfer 2.50 g of ammonium nitrate, and record the displayed mass.
- Dissolve the measured sampleAdd 100.00 mL of 20.0 °C water to the calorimeter, remove the boat from the balance, transfer the weighed solid into the water, and mix.
- Measure the temperature and enthalpyPlace the thermometer, record the final temperature, and compare the measured molar enthalpy with the 25 °C literature value of +25.7 kJ/mol.
On the bench
- 20.0 °C distilled water
- Ammonium nitrate solid
- Weighing boat
- Centigram balance
- Coffee-cup calorimeter
- Digital thermometer
How this is assessed
- Uses the balance and weighing boat to produce a genuine sample-mass measurement.
- Dissolves the measured sample, observes cooling, and obtains the registered molar enthalpy.
Ways to work
- Balance and thermometer readings are exposed as text with units.
- Every weighing, transfer, mixing, and reading action has a keyboard control.