Determination of copper

Iodometric determination of copper is based on the oxidation of iodides to iodine by copper (II) ions, which get reduced to Cu+. Supplies: Flask with copper solution Erlenmeyer Pipette Burette Reactions: 2Cu2+ + 4I- → 2CuI(s) + I2 2S2O32- + I2 → S4O62- + 2I- Procedure: First we added distilled water in blue solution of copper to get total of 100 mL diluted solution. Using the pipette we took 25,0 mL aliquot of the diluted copper solution and poured it into Erlenmeyer. We added concentrated ammonia to neutralize the acid solution and then added 5 mL of concentrated acetic acid and 3 g of solid potassium iodide which made our solution brown. Now we titrated that brown solution using the thiosulfate solution as a titrant until it turned yellow. We added 3 mL of starch solution and titrated it again until the blue colour was gone. Now we added 2 g of potassium thiocyanate and, since the blue colour was back we titrated it again until the solution was white. Participants: Dorotea Gajdek (advanced group) Marina Gapit (advanced group) Juraj Milačić (advanced group) Ema Pollak (beginners group) Valentino Subotičanec (begginers group)