Experiment 8 - Equivalent Weight of an Unknown Acid

Objective

• Prepare a solution of an unknown acid, and then use a standardized sodium hydroxide solution to determine the equivalent weight of the unknown acid.

Introduction

In acid-base reactions the equivalent weight of an acid is the mass of the acid that will react with one mole of sodium hydroxide, NaOH. For hydrochloric acid, HCl, the equivalent weight equals 36.5 grams (the molar mass) since one mole of the acid reacts with one mole of sodium hydroxide.

The equivalent weight of sulphuric acid, H₂SO_4, is 49.0 grams since half a mole of sulphuric acid reacts with one mole of sodium hydroxide.

In this lab, you will be given an acid of unknown identity. The balanced chemical equation for the neutralization of the unknown acid with NaOH has a 1:1 mole ratio of unknown acid:base.