Experiment 16

Objective

To determine the enthalpy of solution of potassium nitrate.

Introduction

The enthalpy of solution is the heat change associated with the dissolution of 1 mole or 1 gram of solute in a solvent. For potassium nitrate, the enthalpy of solution calculation is based on the temperature change observed when 10.1 g of potassium nitrate dissolves in water.

Molecular weight of potassium nitrate: 101 g/molPreparation: 0.1 M solution, where 10.1 g of potassium nitrate is dissolved.

Materials

Chemicals

·       Potassium nitrate

·       Distilled water

Apparatus:

·       250 mL beaker

·       Glass rod

·       Thermometer

·       Stand

·       Balance

Reagent

·       10.1 g potassium nitrate with 89.9 mL distilled water in a 250 mL beaker.

Procedure

1.    Weigh 10.1 g of potassium nitrate using a balance.

2.    Place the 10.1 g of potassium nitrate in a 250 mL beaker.

3.    Secure a thermometer in the beaker using a stand to measure temperature.

4.    Record the initial temperature of the solution.

5.    Add distilled water to the beaker.

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

7.    Stir the solution thoroughly with a glass rod to ensure complete dissolution.

8.    Record the final temperature of the solution.

Observation

The initial temperature is 28.62°C, and the final temperature is 20.38°C.

Enthalpy of Solution Calculation:

Enthalpy of solution= 0.42 × (28.62 − 20.38) × 10KJ/mol = + 34.6KJ/mol

Questions

1.    What is solution temperature?

2.    What is molarity?

3.    What is the enthalpy of potassium nitrate?

4.    How is enthalpy measured?