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The preparation of ions containing vanadium in two oxidation states Aim: - To prepare the two oxidation states of vanadium ions. Introduction:- Vanadium has the chemical symbol V with an atomic number of 23. Vanadium is transition metal and has 4 different oxidation states ranging from 5+ to 2+. The usual source of vanadium in the 5+ oxidation state is ammonium metavanadate (NH4VO3). Ammonium metavanadate can be reduced using zinc and an acid, usually moderately concentrated acid. In the case of my experiment, I will be using sulphuric acid (H2S04) with zinc to reduce ammonium vanadate to an oxidation state of 2+. The exact vanadium ion present in the solution is very complicated and it varies with the pH of the solution. The reaction is done under acidic conditions when the vanadium present is VO2+ and this ion is called dioxovanadium (V) ion. Safety and Precautions:- Step Reason Lab Coats Lab coats must be worn at all times during the experiment in order to prevent the body from getting in contact with any acids or solutions. As most of the chemicals and acids being used in the experiment are toxic, lab coats must be worn at all times to provide full protection to the skin. Goggles Goggles must be worn to protect the eyes from chemicals and acids being used. Full attention to the experiment 100% concentration and attention must be paid while carrying out the experiment in order to prevent errors from occurring. ...read more.


3. Set up a Bunsen burner and gently boil the components in the conical flask for 30 minutes. 4. While the solution is boiling, set up another Bunsen burner at a distance and boil some distilled water in a conical flask to be used in the further experiments. 5. Notice the colour change that occurs when the vanadate solution is boiling and record the observations. 6. Fill a burette with aqueous potassium manganate (VII) and run exactly 25cm3 of KMnO4 into another conical flask. 7. Take a glass funnel and place it on the mouth of the conical flask containing KMnO4. With the help of tongs take some glass wool and place it in the glass funnel covering the conical flask with KMnO4 in it. 8. If the amount of vanadate solution decreases while boiling, add some boiling water to the solution and record the number of times water has been added to the solution at the end. 9. When the vanadate solution has turned pale purple after 30 minutes, take the glass funnel out of the reduction conical flask and filter its contents in to the conical flask with the KMnO4 through the glass wool. Make sure heatproof are worn at all times to protect from hot conical flasks and its boiling contents. 10. Rinse all the contents of the reduction conical flask into the conical flask with KMnO4 and also pour some boiled water on to the glass wool. ...read more.


Thus, while titrating the vanadium mixture, a redox reaction took place between sulphur dioxide and manganate, where sulphur dioxide acted as the reducing agent. This means that the manganate reacted both with sulphur dioxide and vanadium ions and thus a higher volume of MnO4 was required to titrate the vanadium mixture and reach the end point as sulphur dioxide acts as a reducing agent. This resulted in the inaccuracy of the results. * Also, some of the equipments used in the experiment were clumsy and unsteady such as the clamp stands holding the burette due to which it was difficult to read the titre values from the burettes accurately. For example, if the titre value on the burette was 26.70 cm3, it could have been 26.65cm3 but due to the unsteadiness of the burette, inaccurate titre values might have been recorded. * Other experimental error was reading the accurate values off the measuring cylinders. The graduations in the measuring cylinders were quite large and thus reading the measurement values at the eye level was not the best way to measure volumes to the maximum accuracy and precision. Also the values were recorded according to the lower meniscus and therefore it was quite difficult to decide the exact point of the lower meniscus. This could have lead to inaccurate amounts of distilled water to be added to the vanadium mixture. ?? ?? ?? ?? NEELIMA Nathawat, Centre Number: - 10508 Candidate Number: - 2485 1 ...read more.

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