In qualitative analysis. Explain why
The cations of group II are precipitated , in acidic medium while those of group IV in alkaline medium.

Explain the following : Dissociation of H_(2)S is suppressed in acidic medium.

The group II precipitate soluble in yellow ammonium sulphide may be

In equalitative analysis, cations of graph II as well as group IV both are precipitated in the form of sulphides. Due to low value of K_(sp) of group II sulphides, group reagent is H_(2)S in the presence of dil. HC1 , and due to high value of K_(sp) of group IV sulphides, group reagent is H_(2)S in the presence of NH_(4)OH and NH_(4)C1 . In a solution containing 0.1M each of Sn^(2+), Cd^(2+) , and Ni^(2+) ions, H_(2)S gas is passed. K_(sp) of SnS = 8 xx 10^(-29), K_(sp) of CdS = 15 10^(-28), K_(sp) of NiS - 3 xx 10^(-21), K_(1) of H_(2)S = 1 xx 10^(-7), K_(2) of H_(2)S = 1 xx 10^(-14) At what value of pH, NiS will start to precipitate?

In salt analysis. Explain why NH_4Cl is added before the addition of NH_4OH in group III.

The role of NH_(4)Cl in the precipitation of the hydroxides of group III cations is to:

Is it necessary to acidify a solution before group II cations are precipitated with H_(2)S ?

Why dehydration of alcohol takes place in acidic medium generally but not in basic medium

In qualitative analysis of group I radicals, a white precipitate is formed which is insoluble in boiling water but when treated with NH_4 OH it turns black. The precipitate may be

Sometimes no precipitate is obtained even if group V radicals are present why ?

Explain why the elements of the same group exhibit the same chemical behaviour.