posted by Sarah on .
These are what i used.
0.0375M sodium thiosulphate , 2.5% KI .47.2 ml copper sulphate solution.
the average volume of Na2S2O3 is 19.25 cm, i have already calculated the number of moles of thiosulphate which is 7.218 * 10-4 moles of Na2S2O3 and also the number of moles of I2 that reacted with S2O32 which was calculated to be 7.218*10^-4/2 = 3.609 * 10^-4
I have to do the calculations for :
The number of Cu2+ that reacted with I- to produce the number of moles of I2 above
The number of moles of Cu2+ in the volumetric flask
The concentration of Cu2+ in the stock solution
Any kind of help would be really appreciated!
You started in the middle of the question. I'm just guessing that you have performed an experiment in which you determined %Cu in a sample. The equations are Cu^2+ + KI(xs) ==> CuI(s) + I2 and I suppose you titrated the liberated I2 with thiosulfate like this
2S2O3^2- + I2 ==> 2I^- + S4O6^2-
mols S2O3^2-, what you titrated with is M x L = ?. Then convert this to moles Cu.
? mols S2O3^2- x (1 mol I2/2 mol S2O3^2-) x (2 mol Cu/1 mol I2) =? mol Cu.