Determination of the Energy of Solution
This lab will allow you to determine the energy required to dissolve various
compounds in water. With better equipment, this can be used to determine the Heat of
Formation (∆H(f)) For the various compounds produced.
Purpose: Create enthalpy graphs for each of a number of salts by determining the amount
of energy used to dissociate each salt into water.
Materials:
Small test tubes
Thermometer
Water
Salt Samples
HCl soln.
3 Vessels- beakers, flasks, etc.
Procedure:
1. Acquire 2 g samples of each compound, labeling them for future reference.
2. Fill your 2nd smallest beaker with 1 M HCl; fill the others with H2O from
your taps.
3. In the first test tube, place 5 mL of H2O from one of your beakers. You must
now use this beaker for all of your water for the rest of the lab. The other will
be used to rinse the thermometer, etc. off to prevent cross-contamination of
each sample. You must measure this carefully, so you can correctly determine
how many calories are used/ produced by each solution.
4. Place the thermometer GENTLY into the tube; let the thermometer adjust to
the water temperature. Read and record the results.
5. Add the first sample of salt, being careful not to spill salt on the sides of the
tube. Stir or shake gently until the salt is dissolved. DO NOT hold the tubes
near the water; hold them only at the top of the tubes.
6. Watch the thermometer closely, and check for any changes. Record this
information.
7. Rinse the thermometer in HCl, then in the OTHER beaker of water. Dry.
8. Repeat 3-7 until all samples are completed.
9. Complete the data table and create 1 Enthalpy graph (using different colors for
each solution) showing the various ∆H(f) of each salt.