# Concentration cell lower half cell concentration from measured cell potential

I am trying to find the Ksp of silver thiocyanate: AgSCN(s) --> Ag+ (aq)SCN-(aq)

but I need to first prove that the lower [Ag+] = 1.27-12 M, but don't know how to find it.

The data I am given: Volume of 10-4 M Ag+ solution used: 10.00ml

Volume of 1.0 M KSCN added: 50.00ml

Measured cell potential when an Ag(s) electrode was placed into the above mixture, and then joined to the Ag+(0.1M)/Ag(s) half cell: 0.645V

Results: Calculated lower [Ag+] from cell potential: 1.27-12 M

I am suppose to use this equation for the concentration cell: where n is the number of electrons.

So really my question is how I would go about finding the higher concentration of Ag+ and then use that to determine that lower [Ag+] = 1.27-12M

• Can you define what lower and higher mean? A sketch of your cell could be useful. – Burak Ulgut Mar 30 '15 at 8:12
• This is a concentration cell, which has the same components in each half cell, but the concentrations are not standard (1mol/L) and the difference in concentration results in an electrode potential. By higher I mean the half cell with a higher concentration of Ag+ which is the cathode half cell, and the lower concentration half cell is the anode. So the net cell reaction is Ag+(higher)-->Ag+(lower) and thus the Nernst equation is link The idea is that the concentration of SCN- is much larger than the lower concentration of Ag+ – Morrowdox Mar 30 '15 at 8:49