A) silver is immiscible in molten Zn
B) Ag is miscible in NaCN
C) Ag is more miscible in molten Zn than in molten Pb
D) Ag is more miscible in molten Pb in comparison to molten Zn
Correct Answer: C
Solution :
When lead-silver alloy is poor in silver (such as argent ferrous lead or galena), desilverisation of lead is affected by Parkes process. It depends upon the fact that (i) When zinc is added to a melted alloy of silver and lead, zinc takes away silver from the alloy and itself forms an alloy with silver and not with lead because Ag is more miscible in molten Zn than in molten Pb. (ii) Alloy of zinc and silver melts at a higher temperature than lead. (iii) The alloy of silver and zinc is lighter than lead and forms two separate layers. (iv) On distillation of silver and zinc, zinc separates.
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