Melals like Cu, Ag, Zn, Hg and Pb occur in nature as sulphide rather than oxides. Why ?

The cations of these metals i.e. Cu+2, Ag+, Zn+2, Hg+2 (pseudo inert gas configuration), and Pb+2 ( inert gas configuration) have high polarising power and hence can easily polarise the bigger S-2 ion than the smaller O-2 ion. Hence sulphides are more stable than oxides of these metals.

Cu+2, Ag+, Zn+2 and Hg+2 are soft Lewis acids and S-2 is soft Lewis base . Compounds obtained by reaction between soft Lewis acid and soft Lewis base is stable. O-2 is hard Lewis base . Adduct of soft Lewis acid and hard Lewis base is not very stable compounds.

 

Why halogens are insoluble in water ?

Halogens (X2) are "non polar" in nature , they are insoluble in water (polar solvent) but in soluble in non polar solvents  like CCl4, C6H6, and CS2 etc.

(1): But Fluorine is soluble in water due to its high oxidizing nature, decomposition even water and form ozonides oxygen.

(2): To increase the solubility of Iodine in water, potassium iodide (KI) is added

Related Questions:

(1) What are the hydrolysis products of urea ?

(2) CCl4 can not be hydrolysed but SiCl4 can be. Why?

(3) Why PCl3 hydrolysed while NCl3 can not be hydrolysed?

(4) Why SF6 behave inert towards hydrolysis?

(5) Arrange in increasing order of extent of hydrolysis [ CCI4, MgCI2, AICI3, PCl5, SiCI4].

(6) Although Sulphur contain vacant d-orbital but SF6 does not under go hydrolysis. Why ?

(7) Arrange the silicon halides into decreasing order of Lewis acids Character? SiF4, SiCl4, SiBr4, SiI4

Why alums are used as Mordant in dyeing ?

Alums are used as Mordant in dyeing because when fabric to be dyed in dipped a solution of alum and heated with steam. Hydrolysis of [Al(H2O)6]+3 deposite Al(OH)3 into the fibres of materials and the dye is adsorbed on the Al(OH)3.