PbSCN (s) < ----------> Pb2+ (aq.) + 2
SCN- (aq.)
SÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
SÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â
2SÂ Â Â Mol/L of solubility
Ksp = [Pb2+][SCN-]2
In pure water,
2.00 * 10-5 = (S)(2S)2
2.00 * 10-5 = 4S3
S = (2.00 *10-5 / 4 ) 1/3
S = Solubility of lead thiocyanate in pure water = 2.236 *
10-3 M
In KSCN solution,
KSCN -------------> K+ (aq.) + SCN-
(aq.)
1.00Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
1.00Â Â Â Â Â Â Â Â 1.00M
[SCN-] = 1.00 M Since KSCN is completely soluble
assume the [SCN-] is approximately equals to conc. of
SCN- coming from KSCN.
therefore,
Ksp = [Pb2+]SCN-]2
2.00 * 10-5 = (S)(1.00)2
S = solubility of lead thiocyanate in 1.00 M KSCN solution =
2.00 * 10-5 M
