Main group elements and their compounds: Allotropy, synthesis, structure and bonding, industrial importance of the compounds.
|No.of questions appeared||5||4||6||3||2||7||5||2||3||4||5|
1.Among the halides, NCl3(A), PCl3(B) and AsCl3(C), those which produce two different acids.
(a) A and B
(b) A and C
(c) B and C
(d) A, B and C
NCl3+4H2 O —> NH 4OH+3HOCl ; PCl3+ 3H2O —>H PO3+3HCl (two different Acids)
AsCl3+ 3H2 O –> H3 AsO3+3H3 (two different acids)
2.The correct structure of P4 S3 is:
Structure of P4 S3.
3.The reaction that yields Li AlH4 is:
(a) HCl( excess)+ AlCl3+ Li—>
(b) H2+ Al+ Li—>
(c) LiH (excess)+ AlCl3—>
(d) LiH(excess) +Al—>
4.Boric acid is a weak acid in aqueous solution. But its acidity increases significantly in the presence of ethyleneglycol, because
(a) ethylene glycol releases additional H+
(b) B(OH)4- is consumed in forming a compound with ethylene glycol.
(c) ethylene glycol neutralizes H+ released by boric acid.
(d) Boric acid dissociates better in the mixed-solvent.
5.For the deposition of Pb by electroplating, the best suited compound among the following is
PbCl2 and PbSO4 are ionic compounds and insoluble in cold water. Therefore, cannot be used for depositionof Pb and Pb(Et4) is toxic.
6.The correct order of the retention of cations on a sulfonated cation exchange resin column is
(a) Ag+> K+> Na+> Li+
(b) K+> Na+> Ag+> Li+
(c) Li+> Na+> K+> Ag+
(d) Li+> Na+> Ag+> K+
The retention of cation is measured in term of distribution constant K. In general, where K for an ion is large,
there is strong tendency for the resin phase to retain that ion. Therefore, for a typically sulphonated cation exchange resin ,
value of K for a univalent ion decreases in the order
Ag+> Cs+> Rb+> K+>NH4+> Na+> H+> Li +