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JEE Main levelSingle correct optionDifficulty 2 of 3mt021

For which of the following ores is calcination, rather than roasting, the proper preliminary treatment?

AZinc blende, $ZnS$
BGalena, $PbS$
CIron pyrites, $FeS X_{2}$
DMalachite, $CuCO X_{3} \cdot Cu (OH) X_{2}$

Answer: D

Malachite is a hydroxy-carbonate that loses

CO X_{2}

and water on heating in limited air (

CuCO X_{3} \cdot Cu (OH) X_{2} 2 CuO + CO X_{2} + H X_{2} O

), which is calcination. The three sulphides are heated in excess air to oxidise them (roasting).

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