Experiment 14

Objective

To determine the enthalpy of solution of oxalic acid.

Introduction

The enthalpy of solution refers to the heat change when 1 mole or 1 gram of solute dissolves in a solvent. For oxalic acid, when 12.6 g dissolves in water, the enthalpy change can be calculated from the observed temperature difference.

●       Molecular weight of oxalic acid: 126 g/mol

●       Concentration for 0.1 M solution: 12.6 g in a sufficient amount of solvent to make the solution 0.1 M.

Materials

Chemicals

●      Oxalic acid

●      Distilled water

Apparatus

●      250 mL beaker

●      Glass rod

●      Thermometer

●      Stand

●      Balance

Reagents

●      12.6 g oxalic acid and 87.4 g distilled water in a 250 mL beaker.

Procedure

1.    Weigh 12.6 g of oxalic acid using a balance.

2.    Place the oxalic acid in a 250 mL beaker.

3.    Suspend a thermometer in the beaker using a stand and record the initial temperature.

4.    Add distilled water to the beaker containing oxalic acid.

5.    Wait 2–3 minutes for the temperature to stabilize.

6.    Stir the solution with a glass rod to ensure complete dissolution of the oxalic acid.

7.    Record the final temperature of the solution.

Observation

The initial temperature of the solution is 29.46°C, and the final temperature after dissolution is 25.18°C.

Enthalpy of Solution Calculation:

Enthalpy of solution= 0.42 × (29.46−25.18) × 10kJ/mol = + 17.98kJ/mol

Questions

1.    What is solution temperature?

2.    What is molarity?

3.    What is the enthalpy of oxalic acid?

4.    How is enthalpy measured?