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1.

Which of the following reaction is an example of autoreduction?A. `Fe(3)O_(4)+4CO to 3Fe+4CO_(2)`B. `Cu_(2)O+C to 2Cu+CO`C. `Cu^(2+)(aq)+Fe(s) to Cu(s) +Fe^(2+)(aq)`D. `Cu_(2)O+(1)/(2)Cu_(2)S to 3Cu+(1)/(2)SO_(2)`

Answer» Correct Answer - D
(d) `Cu_(2)O+(1)/(2)Cu_(2)S to 3Cu+(1)/(2)SO_(2)`
This reaction includes reduction of copper (I) oxide by copper (I) sulphide. In this process, copper is reduced by itself hence this process is known as autoreduction and the solidified copper. So, obtained is known as blister copper.
Discussion
2.

Zone refining is based on the principle thatA. impurities of low boiling metal can be seperated by distillation.B. impurities are more soluble in molten metal than in solid metal.C. different components of a mixture are differently adsobed on an adsorbentD. vapours of volatile compound can be decomposed in pure metal.

Answer» Correct Answer - B
(b) Zone refining is based on the principle that the impurities are more soluble in molten state than in solid state of the metal. A circular mobile heater fixed at one end of impure metal rod. The molten zone moves along with heater which is moved forward.
As the heater moves forward, the pure metal crystallises out of the melt and the impurities pass on into adjacent molten zone. The process is repeated several times and the heater is moved in the same direction.
At one end, impurities get concentrated. This end is cut off. e.g., germanium, silicon, gallium etc., are refined by this method. 9
Discussion
3.

How do we separate two sulphide ores by Froth Floatation Method? Explain with an example.

Answer» Two sulphide ores can be seperated 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 seperated .
Discussion