Write two basic requirements for refining of a metal by Mond's process and by van Arkel Method.
Two basic requirements are
(i) Metal should form volatile compound with available reagent.
(ii) The volatile compound should be easily decomposable so that it can be recovered easily.
(a) Mond's process includes conversion of Ni to $\mathrm{Ni}(\mathrm{CO})_4$ and then decomposition of $\mathrm{Ni}(\mathrm{CO})_4$ to Ni.
$$\begin{gathered} \mathrm{Ni}+4 \mathrm{CO} \longrightarrow \mathrm{Ni}(\mathrm{CO})_4 \\ \mathrm{Ni}(\mathrm{CO})_4 \xrightarrow{450-470 \mathrm{~K}} \mathrm{Ni}+4 \mathrm{CO} \end{gathered}$$
(b) van Arkel method includes conversion of Zr to volatile $\mathrm{ZrI}_4$ and then decomposition of $\mathrm{ZrI}_4$ to Zr and $\mathrm{I}_2$.
$$\mathrm{Zr}+2 \mathrm{I}_2 \xrightarrow{870 \mathrm{~K}} \mathrm{ZrI}_4 \xrightarrow{2075 \mathrm{~K}} \mathrm{Zr}+2 \mathrm{I}_2$$
Although carbon and hydrogen are better reducing agents but they are not used to reduce metallic oxides at high temperatures. Why?
Because at high temperatures, carbon and hydrogen react with metals to form carbides and hydrides respectively. So, carbon and hydrogen are not better reducing agents to reduce metallic oxide.
How do we separate two sulphide ores by froth floatation method? Explain with an example.
Two sulphide ores can be separated by adjusting the proportion of oil and water or by using depressants, e.g., if an ore contains ZnS and PbS both, a depressant NaCN is added during froth floatation. It forms a complex with ZnS and prevents it from coming into froth. PbS comes into the froth and thus separated.
The purest form of iron is prepared by oxidising impurities from cast iron in a reverberatory furnace. Which iron ore is used to line the furnace? Explain by giving reaction.
(a) Haematite $\left(\mathrm{Fe}_2 \mathrm{O}_3\right)$ ore is used to line the furnace.
(b) $\underset{\substack{\text { Haemattie } \\ \text { lining }}}{\mathrm{Fe}_2 \mathrm{O}_3}+\underset{\begin{array}{c}\text { Impurtilies } \\ \text { (present in cast iron) }\end{array}}{3 \mathrm{C}} \longrightarrow \underset{\begin{array}{c}\text { Wrought } \\ \text { iron }\end{array}}{2 \mathrm{Fe}}+3 \mathrm{CO}$
The mixture of compounds A and B is passed through a column of $\mathrm{Al}_2 \mathrm{O}_3$ by using alcohol as eluant. Compound A is eluted in preference to compound B . Which of the compounds A or B, is more readily adsorbed on the column?
Compounds which are adsorbed to the more extent comes out later while the another one which absorbed to the less extent comes out readily. Since, compound ' $A$ ' comes out before compound ' $B$ ', the compound ' $B$ ' is more readily adsorbed on the column.