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AIM To make samples of the less common oxidation states of vanadium with different colours

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Introduction

________________ Mohamad Zulhilmi bin Azmi 930813-05-5385 Chemistry HL INTRODUCTION Vanadium's ground state electron configuration is [Ar] 3d34s2. When transition elements ionize, they lose their valence s electrons before losing their d electrons. Vanadium has 5 valence electrons that one of the characteristics of transition metal is their ability to adopt multiple oxidation states. Vanadium exhibits four common oxidation states +5, +4, +3, and +2 each of which can be distinguished by its colour. AIM To make samples of the less common oxidation states of vanadium with different colours HYPOTHESIS Different oxidation states of vanadium show distinct colours. One of the special characteristics of transition elements is its ability to form coloured complexes like vanadium. This is because it has variable oxidation numbers. The colours formed are predominantly due to the splitting of the d shell orbitals into slightly different energy levels. As a result, certain wavelengths of energy can be absorbed by the d-block elements (with electrons jumping between these slightly different energy levels), resulting in the complement color being visible. VARIABLE Type of variable Method to handle Independent variable 1. Oxidation number of vanadium Distinct the oxidation state of vanadium by making samples of different oxidation states of vanadium Dependent variable 1. ...read more.

Middle

SAFETY MEASURES Concentrated sulphuric acid solution is corrosive and reacts violently with water. Below action is compulsory: 1. wear safety goggles and gloves; 2. when diluting, add acid to water, not water to acid; 3. mop up small spillages with excess water. TABULATION OF DATA 1. Raw data: Reaction Ammonium Metavanadate (V) + dilute sulphuric acid + concentrated sulphuric acid Observation White solid dissolved to form a yellow solution Reaction : Vanadium(V) + zinc Observation Time intervals(s)(0.2s) Observation 0.0 Yellow solution present 10.0 Green solution formed 20.0 Light blue solution formed 30.0 Dark blue solution formed 40.0 Dark blue solution formed 50.0 Dull grey blue solution formed 60.0 Dull grey blue solution formed 70.0 Green solution formed 80.0 Green solution formed 90.0 Violet solution formed Further reactions: Reaction Observation Vanadium (II) + acidified potassium manganete(VII) Green solution formed Vanadium (V) + sodium sulphite + Vanadium (II) Green solution formed Vanadium (V) + potassium iodide + sodium thiosulphate Light blue solution formed 1. Processed data : Ion (hydrated) VO2+ VO2+ V3+ V2+ Colour yellow Blue green Violet Oxidation state +5 +4 +3 +2 Test Equation of reaction Ammonium Metavanadate (V) + dilute sulphuric acid + concentrated sulphuric acid VO3- (aq) ...read more.

Conclusion

The oxidation states of vanadium subsequently reduced from +5 to +4 followed by +3 and finally +2. The changes in colour explain the reduction process. However, the yellow colour turn green first instead of blue. Actually, the green colour is not the new oxidation state that is +3. It is just a mixture of the original yellow and the blue that is being produced. Acidified potassium manganete (VII) is an oxidising agent which oxidise vanadium(II) to become vanadium(III). The colour change from violet to green explained the increment of oxidation number of vanadium from +2 to +3. EVALUATION A weakness was discovered throughout the experiment regarding the procedure. Firstly, all the apparatus containing vanadium solution was not closed using cotton wool. There is always a possibility for the vanadium solution especially with oxidation states below than +5 to be oxidised by oxygen in the air. To solve this problem, every apparatus containing any oxidation states of vanadium should be close with cotton wool. By using this method, we can avoid or reduce the possibility of re-oxidation of the oxidation states which may affect the colour formed. All in all, this experiment has succeeded to show different colour of distinct oxidation states of vanadium which is one of the special characteristics of transition elements. ...read more.

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