chemistry-class-12-unit-06-chapter-01-isolation-of-metals-l-1-3-aodity5c8fi

<h3 id="successmetal-extraction-or-metallurgysuccess"><Success>Metal extraction or metallurgy</Success></h3>
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<h4 id="some-important-questions-of-metallurgy">Some important questions of metallurgy</h4>
<p><strong>Question</strong> - From what we do isolation or extraction ?</p>
<p><strong>Question</strong> - Is there any difference between ore or mineral ?</p>
<p><strong>Answer</strong> - Yes , ore is mineral from which metal can be extracted conveniently and economically are known as ores</p>
<ul>
<li>
<p>All ores are minerals but reverse is not true</p>
</li>
<li>
<p>Clay is mineral of Al but ores are bauxite and cryolite</p>
</li>
</ul>
<p><strong>Question</strong> Generally ore requires enrichment before extraction why ?</p>
<p><strong>Answer</strong> - It is usually contaminated with earthly or undesired material known as gangue</p>
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<h3 id="successexample-of-some-oressuccess"><Success>Example of some ores</Success></h3>
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<table>
<thead>
<tr>
<th><strong>Metal</strong></th>
<th><strong>Ores</strong></th>
<th><strong>Composition</strong></th>
</tr>
</thead>
<tbody>
<tr>
<td>Aluminium</td>
<td>Bauxite</td>
<td>$AlO_x(OH)_{3-2x}[where  0<x<1]$</td>
</tr>
<tr>
<td>Zinc</td>
<td>Zinc blende or sphalerite calamine zincite</td>
<td>ZnS $ZnCO_3$ ZnO</td>
</tr>
<tr>
<td>Copper</td>
<td>Copper pyrites malachite cuprite copper glance</td>
<td>$CuFeS_2,CuCO_3.Cu(OH)_2,Cu_2O,Cu_2S$</td>
</tr>
<tr>
<td>Iron</td>
<td>Haematite magnetite siderite iron pyrites</td>
<td>$Fe_2O_3,Fe_3O_4,FeCO_3,FeS_2$</td>
</tr>
</tbody>
</table>
<br>
<ul>
<li>Nature of ore $\hspace{2mm} \xrightarrow{governs} \hspace{2mm} Total \hspace{1mm} process \hspace{1mm}of \hspace{1mm} isolation$</li>
</ul>
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<h4 id="successthe-extraction-and-isolation-of-metalssuccess"><Success>The extraction and isolation of metals</Success></h4>
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<p><strong>The extraction and isolation of metals from ores involve the following major steps</strong></p>
<ul>
<li>Concentration of the ore</li>
</ul>
<ul>
<li>Removal of the unwanted materials (example - sand, clays, etc) from the ore is known as concentration , dressing or benefaction</li>
</ul>
<ul>
<li>Isolation of the metal from its concentrated ore</li>
</ul>
<ul>
<li>Conversion into a form which is suitable for reduction (Oxide) followed by readuction</li>
</ul>
<ul>
<li>Purification or refining of the metal</li>
</ul>
<ul>
<li>Distillation , liquation , electrolysis , zone refining vapour phase refining etc</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/chemistry-class-12-unit-06-chapter-01-isolation-of-metals-l-1_3-aodity5c8fi-064-0610.8.jpg"></p>
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<h3 id="successconcentration-of-oressuccess-1"><Success>Concentration of ores</Success></h3>
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<h4 id="types-of-magnetic-materials">Types of magnetic materials</h4>
<ul>
<li>On the basis or magnetic properties material may be called</li>
</ul>
<p>$\quad$ $\swarrow$ $\quad$  $\quad$ $\searrow$</p>
<p>$ Diamagnetic  \quad Paramagnetic $</p>
<p><strong>Diamagnetic</strong></p>
<ul>
<li>Repelled to a point of least magnetic field</li>
<li>Example - Alumina</li>
</ul>
<p><strong>Paramagnetic</strong></p>
<ul>
<li>Attracted to a point of high magnetic field</li>
<li>Example - Ilmenite , Ni , Co , Mn minerals presence of iron can cause paramagnetic behaviour</li>
</ul>
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<h3 id="successleachingsuccess"><Success>Leaching</Success></h3>
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<ul>
<li>
<p>If ore is soluble in  solvent it is an effective method of enrichment</p>
</li>
<li>
<p>Leaching of alumina from bauxite</p>
</li>
<li>
<p>Bauxite (principle ore of aluminium) y contains $SiO_2$ , iron oxides and titanium oxide $(TiO_2)$ as impurities</p>
</li>
<li>
<p>Powered Ore is digested with a concentrated solution of NaOH at 473 - 523 K and 35 - 36 bar pressure</p>
</li>
<li>
<p>$Al_2O_3$ is leached out as sodium aluminate (and $SiO_2$ too as sodium silicate) leaving the impurities behind</p>
<p>$ {Al}_2{O}_3(S) + 2NaOH + 3{H}_2O(l) \rarr 2{Na}{[Al(OH)_4]}(aq)$</p>
</li>
<li>
<p>Aluminate in solution is neutralised by passing $CO_2$ gas and hydrated $Al_2O_3$ is precipitated as</p>
<p>$ 2{Na}{[Al(OH)_4]} + C{O}_2(g) \rarr {Al}_2{O}_3.x{H}_2O(s) +2NaHC{O}_3(aq)$</p>
</li>
</ul>
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<p><img alt="image" src="https://temp-public-img-folder.s3.ap-south-1.amazonaws.com/sathee.prutor.images/subject-images/iitpal/image/chemistry-class-12-unit-06-chapter-01-isolation-of-metals-l-1_3-aodity5c8fi-04.jpg"></p>
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<h3 id="successconcentration-of-oressuccess-3"><Success>Concentration of ores</Success></h3>
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<p><strong>Question</strong> - What happens to silica which is leached with alumina ?</p>
<p><strong>Answer</strong> - The sodium silicate remains in the solution</p>
<ul>
<li>Seeding with Hydrated $Al_2O_3$ , induces the precipitation and increase amount hydrated alumina precipitated</li>
<li>It is filtered , dried and heated to give back pure $Al_2O_3$
${Al}_2{O}_3.x{H}_2O (heat\hspace{2mm} at \hspace{2mm}1470 K)\rarr {Al}_2{O}_3(s) + x{H}_2O(g)$</li>
<li>Silver and gold , leached with a diluted solution of NaCN or KCN in the presence of air (for $O_2$)</li>
<li>$ 4M(s)+ 8CN^-+ 2{H}_2O + {O}_2(g)\rarr 4{[M(CN)_2]}+4{OH}^-$(M=Ag or Au)(Same reaction occurs when M is in combined from)</li>
<li>Recovered by Zn</li>
</ul>
<p>$ 2{[M(CN)_2]}^{+} +Zn \rarr {[Zn(CN)_4)]}^{+} +2M$</p>
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<h3 id="successroastingsuccess"><Success>Roasting</Success></h3>
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<ul>
<li>Ore or ore + additive</li>
<li>In case of ore copper pyrite or chalcopyrite $(CuFeS_2)SiO_2$ is added in roasting</li>
</ul>
<p>$2CuFe{S}_2+{O}_2 \rarr {Cu}_2S+2FeS+S{O}_2$</p>
<p>$2{Cu}_2S+3O_2 \rarr 2{Cu}_2O+2S{O}_2$</p>
<p>$2FeS+3{O}_2 \rarr 2Fe{O} + 2S{O}_2$</p>
<p>$FeO+Si{O}_2 \rarr FeSi{O}_3$</p>
<p>${Cu}_2O+FeS \rarr {Cu}_2S+FeO$</p>
<ul>
<li>Fe is removed as a silicate slag</li>
<li>Reverberatory furnace</li>
</ul>
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