1.

Cinnabar (HgS) and galena (PbS) on roasting often give their respective metals but zinc blende (ZnS) does not . Explain .

Answer»

Solution :On roasting all these sulphide ores are partly converted into their RESPECTIVE OXIDES . Since the oxides of mercury and lead are unstable while that of zinc is stable , therefore , oxides of mercury and lead bring about the reduction of their respective sulphides to the CORRESPONDING metals but zinc oxide does not reduce ZnS to Zn metal
`HgS + underset("(unstable)")(2 HgO) overset(Delta)(to) 3 HG+ SO_(2) ,`
`PbS + underset("(unstable)")(2PbO) overset(Delta)(to) 3 Pb + SO_(2)`
`ZnS + underset("(stable)") (2ZnO) to 3 Zn + SO_(2)`


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