I just need 11 and 12 quickly please. Thank you! 9. (6) Of te follow ing reactio
ID: 1056598 • Letter: I
Question
I just need 11 and 12 quickly please. Thank you!9. (6) Of te follow ing reactions, # I has a smaller K. Construct a statement about about relative stability of umultidentate ligand complexes and briefly explain why the K for i1 is smaller than the K for The concentration of Fe in a solution can be determined by two different methods. Method 1 involves reacting the Fe,. in the solution with standard i and titrating the ecess, with standard thiosulfate treactions1 and 2 below . Method 2 involves a direct titration of the iron solution with a permanganate solution (reaction 3 s below
Explanation / Answer
11. When all Fe3+ reacted and we have I2 in high concentration which combine with I- to give dark brown colour I3- and its colour is easily visible(reaction-1).Now add thiosulphate in this coloured solution and when the colour of solution changes to very weak pale(in this case I3- almost has exhausted and end point is very close), then add starch. adding starch will give very intense blue colour due to formation of starch-iodine complex which is formed by I3- and starch. You must starch only close to end point otherwise added stach earlier would adsorb iodine which from solution and titration result will not be accurate!
12. Let y is the concentration of Fe3+ solution. Then milli moles of Fe3+ in solution = 50*y
From reaction1,it is clear that millimoles of I3- exclusively needed for titration of Fe3+ = 1/2 of millimoles of Fe3+ = 25*y
Total millimoles of I3- = 10*0.25 = 2.5 millimole, so I3- available for reacting with thiosulphate = (2.5 - 25*y)
In reaction with thiosulphate, the molar ratio is 1:2, it means that for each one mol of I3-, 2 mol of thiosulphate needed.
Thiosulphae needed = 34.52* 0.0715 = 2.468
So milli moles of I3- = 1/2 * 2.468 = (2.5 - 25*y), y = 0.05M