Question

Ingat Lake The Per Formationstret Diktera Use the tabel to answer the question a) Should the following equilibria be offset to the left or right 1. Hg(CN)2 + Ca(ClO4)2 + Hg(CIO4)2 + Ca(CN)2 2. [Cu(CH3CN)n]* + [Li(H20)n][Cu(H20)n]* + [Li(CH3CN)n]* (b) What solid compound should be formed from an aqueous solution in which dissolved HgCl2, KI, and KF? (c) In nature, metals can exist as oxidic or sulfidic minerals. What type do you expect for aluminum and cadmium, respectively? Lewissyror och -bases* Hard Syror: H+, Lit, Na+, K+, Be2+, Mg2+, Ca2, Cr2+, Cr3+, Al3+, Borderline Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2', SO2, BBr3 Soft Cut, Agt, Aut, Tl, Hg. Pd24 Cd2+, Pt2+, Hg2+, BH3 SO3, BF3 Baser: F: OH, H20, NH3, CO;2. NO, SO2, Br, N3, N2, H, R: CN, CO, 1, SCN, R3P, NO3, 02., SO42: PO43, C104 C6H5N, SCN, RCN C6H6, RS * The underlined element is the bond atom to which the classification refers.

Answer 1

The HSAB (hard-soft acid base) theory states that hard acid-hard base and soft acid-soft base combinations are more stable and preferrable than hard acid-soft base and soft acid-hard base.

Hard means the species which are small, and have high charge density and have high electronegativity.

Soft  means the species which are large, and have low charge density and generally have low electronegativity.

(a)

Hg(CN)2 + Ca(C104)2 = HgC1O4)2 + Ca(CN)

Here, Ca2+ and ClO4- are hard acid and hard base respectively, & Hg2+ and CN- are soft acid and soft base respectively. Therefore, according to HSAB theory Hg(CN)2 and Ca(ClO4)2 are the more stable and preferred complexes. The equilibrium will be offset to the left side.

(b)

Cu(CH3CN)n]+ + [Li(H2O)n]+ = [Li(CH3CN)n]+ + [Cu(H2O)n]+

Here, Cu+ is larger than Li+, therefore Li+ is hard acid and Cu+ is the comparatively softer acid.

CH3CN coordinates with the metal using the lone pair on the nitrogen atom whereas H2O coordinates with the metal using the lone pair on the oxygen atom. Oxygen has higher electronegativity than nitrogen. Therefore, H2O is harder base than CH3CN. Therefore, the combinations [Cu(CH3CN)n]+ and [Li(H2O)n]+ are more stable. The equilibrium will be offset to the right side.

(b) Complexes made of Hard acid-Hard base combination are ionic in character and hence dissociates into ions and become soluble in dipolar solvents H2O. Whereas the complexes formed by soft-soft combinationv are covalent in nature and hence do not dissociate into ions in H2O and generally are insoluble.

Now, in the solution of HgCl2, KI and KF mixture, Hg+ is a soft acid (larger in size than K+) and I- is softer acid than

F- and Cl- . Therefore, Hg+ and I- will form HgI2 complex which is covalent in nature and hence not soluble in water and hence will form solid ppt.

(c)

Al3+ is a hard acid and Cd2+ is a soft acid. O2- is a hard base and S2- is a soft base.

Therefore, Al3+ will preferrably bind with O2- and will form oxidic minerals. Cd2+ will preferrably bind with S2- and will form sulfidic minerals.