Experiment 7

Title

AN EXPERIMENTAL STUDY OF SOME IMPORTANT ASPECTS OF MANGANESE CHEMISTRY

Introduction

Manganese chemistry is the study of chemical properties of Manganese metal. Manganese is a hard, brittle, grey-white metal and it is one of the most reactive elements on the Periodic Table. It produces hydrogen gas when reacted with water but it forms Mn2+when dissolved in dilute acids and it is used to form MnO2. The permanganates which are deep-purple in colour are produced by oxidation of manganese compounds. The advantage of Manganese metal is that it plays a huge role in the production of steel, that is, it improves the strength and toughness of steel. In this experiment the typical reactions of manganese are performed and different oxidation states are observed. The MnO2 percentage yield is determined in pyrolusite using the oxalate method.

Experimental Procedure

1. An investigation of reaction between MnO4 and oxalate at different conditions.

Sodium oxalate (40 ml) solution was measured into each of 4 different beakers-A, B, C and D. KMnO4 (0.02M, 25 ml) was pipetted into each of another set of 4 different beakers-a, b, c and d, followed by diluted H2SO4 (10 ml).

* Room temperature investigation

Beaker (a) was placed next to (A). MnSO4 (1 ml) solution was poured into beaker (B) and (b) placed next to it. The contents of (a) and (b) were simultaneously poured into (A) and (B), respectively. The stopwatch was started at the same time. The contents of mixtures in beakers (A) and (B) were stirred. The times were noted when the purple colour was observed disappearing into light brown colour and also when the brown colour was changing to colourless in each beaker.

* Investigation at 60°C

Beaker (C) was placed in water at ± 70°C and left for 10 minutes. Contents of beaker (c) were poured into that of (C) while stirring and starting the stopwatch. The time were noted when the colour change occurred.

2. Determination of the % MnO2 in pyrolusite...