91.

The chemical composition of slag formed during the smelting process in the extraction of copper is

• FeSiO₃

• CuFeS₂

• Cu₂S + FeO

• Cu₂O + FeS

Silver ornaments tum black in the atmosphere. It is due to the formation of

• Ag₂O, Ag₂S

• AgNO₃, Ag₂S

• Ag(OH), Ag₂CO₃

• Ag, Ag₂O

The age of most ancient geological formation is estimated by

• carbon dating

• potassium-argon dating

• radium-radon dating

• uranium-lead dating

Malachite decomposed to give A+CO₂+ H₂O and compound A on reduction with carbon gives CO+B. Here, A and B are

• CuO, Cu

• Cu₂O, CuO

• Cu₂O, Cu

• CuCO₃, Cu

Among the following statements, the incorrect one is

• Calamine and siderite are carbonates

• Argentite and cuprite are oxides

• Zinc blende and pyrites are sulphides

• Malachite and azurite are ores of copper

Calcination is used in metallurgy for removal of

• water and sulphide

• water and CO₂

• CO₂ and H₂S

• H₂O and H₂S

In blast furnace, the highest temperature is in

• reduction zone

• slag zone

• fusion zone

• combustion zone

In the metallurgy of iron, when limestone is added to the blast furnace, the calcium ions are removed as

• slag

• gangue

• metallic Ca

• CaCO₃

Of the following substances, the one which does not contain oxygen is

• bauxite

• dolomite

• cryolite

• epsomite

A smuggler could not carry gold by depositing iron on gold surface since

• gold has higher standard reduction potential than iron

• gold has lower standard reduction potential than iron

• gold is denser

• iron rusts