reaction

is Pbcl₂ soluble in excess of KCN ????????????

why roasting is done below melting point of metal ans in calcination below fusion temperature ???????

is there any difference between pyrites and marcasite ????????

Q.1) Perhaps , when dis reaction takes place in aqueous solution , HCl splits into H⁺ and Cl^-

and reacts with chromate ion to evolve chromyl chloride gas - CrO₂Cl₂ (reddish gas )

Q.2) yes it is. forms a soluble complx [Pb(CN)₄]^2- .

Q.3)just a tryperhaps as by heating above melting point sulphides will melt away as sulphides

only as the temperature doesn't remain optimum for oxidation into oxides.

Q.4) Marcasite is often mistakenly confused with pyrite, but marcasite is lighter and more brittle. Specimens

of marcasite often crumble and break up due to the unstable crystal structure, and it is this crystal

structure that is the main difference between marcasite and pyrite. Though marcasite has the same

chemical formula as pyrite, it crystallizes in a different crystal system, thereby making it a separate mineral.

In jewelry, pyrite used as a gem is improperly termed "marcasite". True marcasite is never used as a gem,

due to its brittle and chemically unstable structure, while pyrite is.