The method of zone refining of metals is based on the principle of

• greater noble character of the solid metal than that of the impurity

• greater solubility of the impurity in the molten state than in the solid

• greater mobility of the pure metal than that of impurity

• higher melting point of the impurity than that of the pure metal 

In the extraction of copper, metal is formed is the Bessemer converter due to reaction

• 2Cu₂S + 2Cu₂O  → 6Cu + SO₂

• 2Cu₂O → 4Cu + O₂

• Cu₂S → 2Cu + S

• Fe + Cu₂O → 2Cu + FeO

Excess of KI reacts with CuSO₄ solution and then Na₂S₂O₃ solution is added to it. Which of the statements is incorrect for this reaction ?

• Cu₂I₂ is formed

• CuI₂ is formed

• Na₂S₂O₃ is oxidised

• Evolved I₂ is reduced

Copper matte contains .....

• Cu₂O, Cu₂S

• Cu₂O, FeO

• Cu₂S, FeS

• Cu₂S, FeO

Which of the following is an alum?

• Na·AlO₂

• Na₂SO₄·Al₂(SO₄)₃·24H₂O

• KCl·MgCl₂·6H₂O

• FeSO₄ ·(NH₄)₂SO₄·6H₂O

Mixtur e of MgCl₂, and MgO is called :

• Portland cement

• Sorrel's cement

• double salt

• none of these

The process of zinc-plating on iron sheet is known as:

• annealing

• roasting

• galvanization

• smelting

Bronze is a mixture of

• Pb+ Sn

• Cu+ Sn

• Cu + Zn

• Pb+ Zn

Therrnite process is used in reduction of

• Cr₂O₃

• Al₂O₃

• PbO₂

• CuO

Wolframite ore is separated from tin stone ore by the process of

• roasting

• electromagnetic

• smelting

• calcination