Question

Complexes formed in the following methods are–
(I) Mond's process for purification of nickel
(II) Removal of unreacted AgBr from photographic plate
(III) Removal of lead poisoning from the body
(IV) Cyanide process for extraction of silver
(V) Froth floatation process for separation of ZnS from galena ore by using depressant.

• A.
  $\left(i\right)Ni\left(CO{)}_4\right(ii\left)\right[Ag\left(CN{)}_2{]}^{–}\right(iii\left)\right[Pb\left(EDTA\right){]}^{2-}\left(iv\right)\left[Ag\right(CN{)}_2{]}^{–}\left(v\right)\left[Zn\right(CN{)}_2]$
• B. $\left(i\right)Ni\left(CO{)}_4\right(ii\left)\right[Ag\left(S_2{O}_3{)}_2{]}^{3-}\right(iii\left)\right[Pb\left(EDTA\right){]}^{2-}\left(iv\right)\left[Ag\right(CN{)}_2{]}^{–}\left(iv\right)\left[Zn\right(CN{)}_4{]}^2$
• C. $\left(i\right)Ni\left(CO{)}_6\right(ii\left)\right[Ag\left(S_2{O}_3{)}_2{]}^{3-}\right(iii\left)\right[Pb\left(EDTA\right){]}^{4-}\left(iv\right)\left[Ag\right(CN{)}_2{]}^{–}\left(v\right)\left[Pb\right(CN{)}_6{]}^{4-}$
• D. $\left(i\right)Ni\left(CO{)}_4\right(ii\left)\right[Ag\left(S_2{O}_3\right){]}^{–}\left(iii\right)\left[Pb\right(EDTA\left){]}^{2-}\right(iv\left)\right[Ag\left(CN{)}_4{]}^{3-}\right(v\left)\right[Pb(CN{)}_4{]}^{2-}$

Answer 1

The correct option is B $\left(i\right)Ni\left(CO{)}_4\right(ii\left)\right[Ag\left(S_2{O}_3{)}_2{]}^{3-}\right(iii\left)\right[Pb\left(EDTA\right){]}^{2-}\left(iv\right)\left[Ag\right(CN{)}_2{]}^{–}\left(iv\right)\left[Zn\right(CN{)}_4{]}^2$

I. Mond's Process for purification of nickel is based on the formation and decomposition of the complex $\left[Ni\right(CO{)}_4]$.
The reaction is represented as
$Ni+4CO\uparrow \stackrel{{50}^{\circ }}{\to }\left[Ni\right(CO{)}_4]\stackrel{{230}^{\circ }}{\to }Ni+4CO\uparrow$
II. The photographic plate film involves the dissolution of unexposed silver bromide in hypo solution according to the following reaction.
$AgBr+2N{a}_2{S}_2{O}_3\to N{a}_3\left[Ag\right(S_2{O}_3{)}_2]+NaBr$
III. Lead poisoning in the human body can be removed by chelating ligand EDTA (ethylenediamine tetraacetate). EDTA has the ability to bind lead tightly and is more effective than other common chelators.
$P{b}^{2+}EDT{A}^{4-}\to \left[Pb\right(EDTA{)}^{2-}]$
IV. Cyanide Process from the extraction of silver are as follows: -
$2Ag+4NaCN+H_{2}O+\frac{1}{2}{O}_2\to 2Na\left[Ag\right(CN{)}_2]+2NaOH$
i.e., silver form complex salts with $C{N}^{-}$ ion.
V. PbS can be separated from ZnS in the presence of CN^– ion of NaCN.
It depresses the floatation property of ZnS by forming a complex $\left[Zn\right(CN{)}_4{]}^{2-}$.
The reaction is
$ZnS+C{N}^{–}\to \left[Zn\right(CN{)}_4{]}^{2-}$
Here, $C{N}^{-}$ion is used as depressant.