Experiment 57

Objective

To identify the presence of magnesium ions in a sample by observing the formation of a white precipitate upon reaction with ammonium carbonate.

Introduction

Magnesium salts react with ammonium carbonate to form a white precipitate composed of a mixture of magnesium carbonate and magnesium hydroxide.

Reaction:

MgSO4 ​+ 2(NH4​)2​CO3 ​+ 2H2​O → Mg(OH)2 ⋅ MgCO3 ​↓ + 2(NH4)2​SO4 ​+ H2​CO3​

Materials

Chemicals

●      Magnesium sulfate (MgSO₄)

●      Ammonium carbonate ((NH₄)₂CO₃)

●      Distilled water

Apparatus

●      Test tube

●      Test tube holder

Reagents

●      3–4 ml of the magnesium sample solution in a test tube

●      5% ammonium carbonate solution prepared in a 250 ml beaker

Procedure

1.    Place 5–6 ml of the magnesium sample solution in a test tube.

2.    Add a small amount of ammonium carbonate to the test tube.

3.    Observe and record any changes, specifically noting the formation of a white precipitate.

Observation

A white precipitate forms upon the addition of ammonium carbonate, indicating the presence of magnesium ions as a mixture of magnesium carbonate and magnesium hydroxide.

Questions

1.    What is  magnesium salt?

2.    What reagent is used in the magnesium test?

3.    How is ammonia identified?

4.    What color is observed during the magnesium test?