Experiment 111

Objective

To prepare a 250 mL solution of 0.05 M (1/20 M) oxalic acid.

Introduction

Oxalic acid is a primary standard and can be used to prepare a standard solution by dissolving a fixed amount in distilled water. The molecular weight of oxalic acid (COOH-CHOH-CHOH-COOH is 126 g/mol. For a 1 M solution, 126 g of oxalic acid is required per liter. For a 0.05 M solution in 250 mL, the required mass is calculated as follows:

126 x 250 / 20 x 1000 = 1.575 g of oxalic acid

Materials

Chemicals

·       Oxalic acid

·       Distilled water

Apparatus

·       250 mL volumetric flask

·       Funnel

·       Weighing bottle

·       Balance

Procedure

1.    Clean and dry a 250 mL volumetric flask thoroughly.

2.    Weigh out exactly 1.575 g of oxalic acid using a weighing bottle and a balance.

3.    Transfer the oxalic acid into the flask using a funnel.

4.    Add distilled water to the flask gradually, swirling to dissolve the oxalic acid.

5.    Fill the flask to the 250 mL mark with distilled water.

6.    Mix the solution thoroughly to ensure the oxalic acid is evenly dissolved.

Observation

The solution of oxalic acid appears clear, indicating complete dissolution of 1.575 g of oxalic acid in 250 mL of distilled water.

Questions

1.    What is a primary standard substance?

2.    What is a primary standard solution?

3.    What is a 0.05 M oxalic acid solution?

4.    What is the molecular weight of oxalic acid?

5.    What is the solute in this solution?

6.    What is the solvent in this solution?

7.    What defines a solution?