Group 1 solution

Pb2+, Hg2+, and Ag2+ make up Group 1 solution. The separation begins with the addition of 5M HCL, which produces a precipitate that can contain lead chloride; the solid is then cleaned with water (5 drops of hot water). The centrifuge and wash water are easily removed. Pb2+, PbCl+, and chloride ions can be present in the supernatant. The occurrence of Pb2+ is confirmed by the addition of 6M HOAc and some decreases of CrO42- sol, which results in the forming of a yellow or orange precipitate. AgCl and Hg2Cl2 may be present in the other precipitate. Washing is repeated until the wash water is cloudy, and then 15M NH3 is applied and stirred into the remaining ppt. The supernatant may contain Pb2+, PbCl+, and chloride ions. Addition of 6M HOAc and several drops of CrO42- sol and hence formation of a yellow or orange precipitate confirms the presence of Pb2+.The other precipitate may contain AgCl and Hg2Cl2. Washing is repeated until the wash water is faint in cloudiness and then 15M NH3 is added to the remaining ppt an stirred. The supernatant may contain Ag(NH3)2+.the centrifuge forms a black ppt of HgNH2Cl and Hg. The black ppt confirms presence of Hg22+

Post Lab Questions

LiCl has lowest molar solubility. This is due to its high lattice energy. Dissociation of LiCl is very tough. Solubility will be mostly less than 1. In water solubility is 0.4 mol/l

Given that the equilibrium constant of dissociation of K2S is

1.0×10-20=

CASE 1 : when pH is 3

[H+]=10-3

-log [H+] =pH

From (1) 1.0×10-20=

=

=1015×1.0

b) Case ii : when pH is 11

[H+]=10-11

1.0×10-20 =

=

=10

3. For unknown solute, we don’t know the degree of dissociation or degree of association.Solute particles may associate or dissociate and change the number of moles for particles (n).In case of association, calculated value of n will be lesser than actual value of n and when we try to find Molar mass from its weight, value of Molar mass will be higher than actual value.In case of dissociation, calculated value of n will be greater than actual value of n and when we try to find Molar mass from its weight, value of Molar mass will be lower than actual value.