Chemistry - Metallurgy Question with Solution | TestHub

Roasting ($x=7$): Performed by heating in the presence of air. All 7 minerals (sulfides, carbonates, and sulfates) decompose or react to yield metal oxides under these conditions.

Calcination ($y=5$): Performed by heating in the absence/limited supply of air. Only the 5 carbonates and hydrated sulfates (Calamine, Dolomite, Malachite, Epsom salt, and Green vitriol) decompose to form metal oxides, while sulfides ($C{u}_{2}S$, $ZnS$) do not.

Calculation: $x+y=7+5=12$.