Heat of Solution Lab

Intro: This lab investigates the heat of solution of two compounds – sodium thiosulfate and sodium acetate. Heat of solution can be measured in J/g and be used as a means to compare materials for effectiveness when used for such things as heating pads and ice packs.

Objective: You figure this out.

Procedure:

1.  Read procedure and create a data table to represent the information gathered.

2.  Using a weigh tray, mass approximately 10g of Na2S2O3∙5H2O (sodium thiosulfate). Record the exact mass.

3.  Label this trial 1, and set it aside.

4.  Repeat steps 3-5 for the following

  1. 10g of NaC2H3O2, (sodium acetate), label the test tube trial 2.
  2. 10g NaOH, labeled trial 3.

5.  Measure 75.0 mL of cold water into a graduated cylinder. Pour this into the calorimeter and measure the temperature. Be sure to wait for the fluid level in the thermometer to stop moving. This takes about a minute.

6.  Gently pour the contents of the first dish into the calorimeter. Put the lid on it and gently swirl the calorimeter. Record the highest or lowest temperature the solution reaches in five minutes.

7.  Clean and dry the calorimeter and repeat step 6 for the other trials.

Data:

Construct a data table that includes the name of the substances, the trial number, the initial temperature, final temperature, amount of solid added, and temperature change.

Data Analysis:

1.  Calculate the change in heat energy of the water (which equals the heat of solution for each material) for each trial.

2.  Calculate the heat of solution for each material per gram.

3.  Calculate the heat of solution for each material per mole.

4.  The accepted value of heat of solution for sodium thiosulfate is 270J/g and

-44.51 kJ/mol for sodium hydroxide. Use this to calculate percent error for these two compounds.

Conclusion:

Report the enthalpy values for each material and describe their meanings.

Be sure to use the terms enthalpy, endothermic, exothermic, system and surroundings.