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Introduction to titration of copper.

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INTRODUCTION Copper was discovered by chance over 11,000 years ago and today remains one of the most versatile metals on earth1. It is for this reason that it remains invaluable to mankind in a variety of applications from power transmission to micro- electronics. Copper is generally found as the di-valent cation, copper (II) or mono-valent ion, copper (I). At low concentrations, copper is an essential element but is toxic at high levels2 especially in water as it poses serious environmental and human health hazards. Industries involved in metal processing must therefore pre treat and/or detoxify the metal rich effluents before discharging them into the environment3 . As well as removing water pollution, economic benefits ensue from this process, due to the high cost of copper on the World markets. The following techniques can therefore be used to detect the presence of copper ions in water or solutions: TITRATION METHOD It involves a reduction-oxidation titration. Copper(II) ions react with excess iodide ions forming a copper (II) iodide precipitate and molecular iodine. 2Cu2+(aq) + 4I-(aq) 2CuI(s) + I2(aq) The iodine is then titrated against a standard solution of sodium thiosulphate in the presence of a starch indicator. I2 (aq) + 2S2O32-(aq) 2I-(aq) + S4O62-(aq) An alternative to this would be the titration of copper (II) ions against a solution of EDTA using Fast Sulphon F as an indicator. ...read more.


If in solution form, collect on absorbent material and store as a hazardous waste. MAKING UP OF SOLUTIONS To make up 1 litre of a molar solution, the relative molecular mass(RMM) of the solute is to be dissolved in a litre of distilled water. A standard volumetric flask is used. The solute is dissolved in a beaker of water to ensure that it is easily soluble. Using a funnel (so as to avoid spillage), the solution formed is added to the volumetric flask. The empty beaker should be rinsed out with distilled water so as to ensure that all of the dissolved solution has gone into the flask. This is done as it ensures that the concentration is the one required rather than a weaker one. When filling up the volumetric flask, the bottom of the meniscus should touch the line on the neck of the flask. The last cm3 must be added using a dropping pippette as this increases accuracy. Once the exact amount of water is in the volumetric flask, shaking of the solution is necessary so as to ensure that the entire solid is dissolved. Copper Sulfate I am making up 1 litre of a 0.05 molar solution for the colorimetric method. Copper Sulfate has a relative molecular mass of 249.68g. Therefore, in order to make up 1litre of 0.05M, I will have to dissolve 249.68g x 0.05 = 12.48g in a litre of distilled water. ...read more.


1.5cm x 1.5cm Filter paper strips, 2cm x 15cm Copper wire with alligator clips at each end Voltmeter Emery paper Canvas gloves Distilled water 200 cm3 1M Sodium sulfate 200cm3 1M Copper (II) sulfate 100cm3 1M Sodium Sulfate Method: The metal strips were polished using emery paper, rinsed with distilled water and then dried. This was done to ensure that the metal surfaces were free from any oxides that may have formed thereby providing a clean surface for reactions. The copper(II) sulfate, sodium sulfate and distilled water were placed in their own burettes (these are used as they allow the quantity of the solutions to be measured accurately). A funnel was used to ensure that there was no spillage. The volumes in the burettes were then set to 50cm3 by letting any excess solution out through the bottom and into a beaker. This was done until the bottom of the meniscus was laying on the 50cm3 line. The standard run used 50cm3 of copper (II) sulfate and 50cm3 of zinc sulfate. 1. Measure out 50cm3 of copper (II) sulfate into one of the 150cm3 beakers. 2. Dip a copper strip into the solution and attach a crocodile clip to it. This forms the copper half cell. 3. Measure out 50cm3 of zinc sulfate into another beaker, dip a zinc strip into it and attach the other crocodile clip to it. This forms the zinc half cell. 4. 5. ...read more.

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