Answer
Verified
387.6k+ views
Hint: Silver is generally found in combined states and its common ore is silver glance or Argentite. This ore contains impurities which have to be removed before metal can be extracted. This impure ore is treated with acid or base so that the ore particles dissolve while impurities do not.
Complete step by step answer:
The important ore of silver is ${\text{A}}{{\text{g}}_2}{\text{S}}$ (Argentite) from which silver can be extracted in the following steps-
The finely powdered ore is concentrated by the froth floatation process which is based on wettable properties of ores and the impurities associated with them.
It is then treated with $5$% dilute solution of sodium cyanide $\left( {{\text{NaCN}}} \right)$ and air is passed into the solution. The precipitate of silver cyanide is formed.
${\text{A}}{{\text{g}}_2}{\text{S + NaCN}} \rightleftharpoons {\text{2AgCN + N}}{{\text{a}}_2}{\text{S}}$
The precipitate of silver cyanide initially dissolves in excess of sodium cyanide to form soluble complex-sodium argento cyanide.
${\text{A}}{{\text{g}}_2}{\text{S + NaCN}} \to {\text{Na}}\left[ {{\text{Ag}}{{\left( {{\text{CN}}} \right)}_2}} \right]$
The oxygen present in the air converts sodium sulphide to sodium sulphate and as a result the reaction proceeds in forward direction and backward reaction is prevented.
$4{\text{N}}{{\text{a}}_2}{\text{S + 5}}{{\text{O}}_2}{\text{ + 2}}{{\text{H}}_2}{\text{O}} \to {\text{2N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4}{\text{ + 4NaOH + 2S}}$
The solution is filtered to remove the insoluble impurities. It is treated with a more electropositive metal like zinc which can easily displace silver from the complex and silver is obtained in the form of precipitate.
$6\% $ ${\text{2Na}}\left[ {{\text{Ag}}{{\left( {{\text{CN}}} \right)}_2}} \right] + {\text{Zn}} \to {\text{N}}{{\text{a}}_2}\left[ {{\text{Zn}}{{\left( {{\text{CN}}} \right)}_2}} \right] + 2\mathop {{\text{Ag}}}\limits_{{\text{ppt}}{\text{.}}} $
This ppt. is purified by an electrolytic method in which cathode is pure silver, anode is impure silver. The electrolyte used is ${\text{AgN}}{{\text{o}}_3}$ with $1 \% {\text{HN}}{{\text{O}}_3}$. On passing current, pure silver gets deposited at cathode while impurities get deposited at anode.
Hence pure silver is obtained by this method from argentite.
Additional Information:
Silver has many uses-
Silver is used in manufacture of coins, ornaments and jewelry due to its malleability, ductility and resistance to atmospheric oxidation.
It is used in fabricating printed electrical circuits due to its electrical and thermal conductivity.
Note:
Argentite can only exist above the temperature of ${173^ \circ }{\text{C,}}{177^ \circ }{\text{C,}}{179^ \circ }{\text{C}}$. When it cools down to ordinary temperature it turns into monoclinic polymorph called acanthite. It reduces metal availability and toxicity in contaminated soils. It is also used as a polish in sterling silver.
Complete step by step answer:
The important ore of silver is ${\text{A}}{{\text{g}}_2}{\text{S}}$ (Argentite) from which silver can be extracted in the following steps-
The finely powdered ore is concentrated by the froth floatation process which is based on wettable properties of ores and the impurities associated with them.
It is then treated with $5$% dilute solution of sodium cyanide $\left( {{\text{NaCN}}} \right)$ and air is passed into the solution. The precipitate of silver cyanide is formed.
${\text{A}}{{\text{g}}_2}{\text{S + NaCN}} \rightleftharpoons {\text{2AgCN + N}}{{\text{a}}_2}{\text{S}}$
The precipitate of silver cyanide initially dissolves in excess of sodium cyanide to form soluble complex-sodium argento cyanide.
${\text{A}}{{\text{g}}_2}{\text{S + NaCN}} \to {\text{Na}}\left[ {{\text{Ag}}{{\left( {{\text{CN}}} \right)}_2}} \right]$
The oxygen present in the air converts sodium sulphide to sodium sulphate and as a result the reaction proceeds in forward direction and backward reaction is prevented.
$4{\text{N}}{{\text{a}}_2}{\text{S + 5}}{{\text{O}}_2}{\text{ + 2}}{{\text{H}}_2}{\text{O}} \to {\text{2N}}{{\text{a}}_2}{\text{S}}{{\text{O}}_4}{\text{ + 4NaOH + 2S}}$
The solution is filtered to remove the insoluble impurities. It is treated with a more electropositive metal like zinc which can easily displace silver from the complex and silver is obtained in the form of precipitate.
$6\% $ ${\text{2Na}}\left[ {{\text{Ag}}{{\left( {{\text{CN}}} \right)}_2}} \right] + {\text{Zn}} \to {\text{N}}{{\text{a}}_2}\left[ {{\text{Zn}}{{\left( {{\text{CN}}} \right)}_2}} \right] + 2\mathop {{\text{Ag}}}\limits_{{\text{ppt}}{\text{.}}} $
This ppt. is purified by an electrolytic method in which cathode is pure silver, anode is impure silver. The electrolyte used is ${\text{AgN}}{{\text{o}}_3}$ with $1 \% {\text{HN}}{{\text{O}}_3}$. On passing current, pure silver gets deposited at cathode while impurities get deposited at anode.
Hence pure silver is obtained by this method from argentite.
Additional Information:
Silver has many uses-
Silver is used in manufacture of coins, ornaments and jewelry due to its malleability, ductility and resistance to atmospheric oxidation.
It is used in fabricating printed electrical circuits due to its electrical and thermal conductivity.
Note:
Argentite can only exist above the temperature of ${173^ \circ }{\text{C,}}{177^ \circ }{\text{C,}}{179^ \circ }{\text{C}}$. When it cools down to ordinary temperature it turns into monoclinic polymorph called acanthite. It reduces metal availability and toxicity in contaminated soils. It is also used as a polish in sterling silver.
Recently Updated Pages
Basicity of sulphurous acid and sulphuric acid are
Three beakers labelled as A B and C each containing 25 mL of water were taken A small amount of NaOH anhydrous CuSO4 and NaCl were added to the beakers A B and C respectively It was observed that there was an increase in the temperature of the solutions contained in beakers A and B whereas in case of beaker C the temperature of the solution falls Which one of the following statements isarecorrect i In beakers A and B exothermic process has occurred ii In beakers A and B endothermic process has occurred iii In beaker C exothermic process has occurred iv In beaker C endothermic process has occurred
What is the stopping potential when the metal with class 12 physics JEE_Main
The momentum of a photon is 2 times 10 16gm cmsec Its class 12 physics JEE_Main
How do you arrange NH4 + BF3 H2O C2H2 in increasing class 11 chemistry CBSE
Is H mCT and q mCT the same thing If so which is more class 11 chemistry CBSE
Trending doubts
How do you solve x2 11x + 28 0 using the quadratic class 10 maths CBSE
Which type of bond is stronger ionic or covalent class 12 chemistry CBSE
What organs are located on the left side of your body class 11 biology CBSE
Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE
Difference Between Plant Cell and Animal Cell
How fast is 60 miles per hour in kilometres per ho class 10 maths CBSE
Fill the blanks with the suitable prepositions 1 The class 9 english CBSE
The Equation xxx + 2 is Satisfied when x is Equal to Class 10 Maths
When people say No pun intended what does that mea class 8 english CBSE