February 23, 2017

Homework Help: chemistry

Posted by tara on Monday, April 4, 2011 at 6:51pm.

A 1.2431 -g alloy sample was analyzed for its copper content iodometrically. The alloy was dissolved in hot, concentrated nitric acid and prepared for analysis. The addition of excess KI(aq) solution precipitated the copper as cuprous iodide and liberated elemental iodine according to the following reaction:

Cu2+(aq) + Iā€“(aq) → CuI(s) + I2(aq)

The liberated iodine was titrated against a standard thiosulfate solution until the disappearance of the blue starch-iodine indicator complex according to

I2(aq) + 2S2O32ā€“(aq) → 2Iā€“(aq) + S4O62ā€“(aq)

Calculate the percent copper in the sample if 26.41 mL of a 0.2300 M thiosulfate solution was required to react with the liberated iodine.

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