111.
Sometimes it is possible to separate two sulphide ores by adjusting the proportion of oil to water or by using depressants. When a depressant $$NaCN$$ is added to an ore containing $$ZnS$$ and $$PbS,$$ what is the correct observation?
A
$$NaCN$$ prevents $$PbS$$ from coming to the froth but allows $$ZnS$$ to come with froth.
B
$$NaCN$$ prevents $$ZnS$$ from coming to the froth but allows $$PbS$$ to come with froth.
C
$$NaCN$$ prevents frothing of both $$ZnS$$ and $$PbS,$$ hence no froth is formed.
D
$$NaCN$$ does not act as depressant hence a mixture of $$PbS$$ and $$ZnS$$ is found in froth.
Answer :
$$NaCN$$ prevents $$ZnS$$ from coming to the froth but allows $$PbS$$ to come with froth.
114.
In electro-refining of metal the impure metal is made the anode and a strip of pure metal, the cathode, during the electrolysis of an aqueous solution of a complex metal salt. This method cannot be used for refining of
Calcination is the process of converting an ore into its oxide by heating it strongly below its melting point either in absence or limited supply of air. It is usually done to convert metal carbonates and hydroxides to their respective oxides.
\[\begin{align}
& \underset{\text{Limestone}}{\mathop{CaC{{O}_{3}}}}\,\xrightarrow{\Delta }\underset{\begin{smallmatrix}
\text{Calcium} \\
\,\,\,\text{oxide}
\end{smallmatrix}}{\mathop{CaO}}\,+C{{O}_{2}}\uparrow \\
& CuC{{O}_{3}}.Cu{{\left( OH \right)}_{2}}\xrightarrow{\Delta }2CuO+{{H}_{2}}O\uparrow +C{{O}_{2}} \\
\end{align}\]
$$Zr$$ and $$Ti$$ are purified by van-Arkel method.
\[\underset{\text{Impure}}{\mathop{Zr}}\,+2{{I}_{2}}\xrightarrow{600{{\,}^{\circ }}C}Zr\,{{I}_{4}}\xrightarrow{1800{{\,}^{\circ }}C}\underset{\text{Pure}}{\mathop{Zr}}\,+2\,{{I}_{2}}\]
This method is useful for removing all the oxygen and nitrogen present in the form of impurity in certain metals like $$Zr$$ and $$Ti.$$
118.
An ore of tin containing, $$FeCr{O_4}$$ is concentrated by
Purification of aluminium by electrolytic refining is known as Hoope’s process. By this process 99.9% pure aluminium metal is obtained. The cell used for this process consist of three layers. In this cell pure $$Al$$ acts as cathode and anode is made up of impure $$Al.$$