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51.

Iron pipes lying under acidic soil are often attached to blocks of magnesium for protection from rusting. Magnesium offers protection to iron against corrosion because it

A.	is lighter than air	B.	is more readily converted into positive irons
C.	prevents air from reaching the surface of iron	D.	forms a corrosion-resistant alloy with iron

52.

Electrochemical corrosion processes

A.	are accempanied by a flow of current from anodic to cathodic areas in the electrolyte	B.	are accompanied by a flow of current from cathodic to anodic areas in the electrolyte
C.	involve exchange of protons	D.	none of the above

53.

Carbon content of

A.	steel is in between those of cast iron and wrought iron	B.	cast iron is in between those of steel and wrought iron
C.	pig iron is in between those of steel and wrought iron	D.	wrought iron is in between those of steel and cast iron

54.

Percentage of carbon is same in

A.	cast iron and pig iron	B.	cast iron and steel
C.	pig iron and steel	D.	pig iron and wrought iron

55.

Cast iron is obtained by remelting

A.	pig iron and pouring into moulds	B.	steel and pouring into moulds
C.	wrought iron and pouring into moulds	D.	iron ore and pouring into moulds

56.

Which of the following is the least pure from of iron?

A.	Pig iron	B.	Wrought iron
C.	Steel	D.	Bessemer iron

57.

Which of the following statements is not correct?

A.	Rusting of iron can be stopped by carbon dioxide	B.	Rusting of iron takes place in moist air
C.	Rusting of iron produces hydrated iron (III) oxide	D.	Rusting of iron is electrochemical in nature

58.

The process of protection of iron by coating with zinc is called

A.	tempering	B.	galvanizing
C.	nitriding	D.	smelting

59.

Electrochemical reactions at the anode are oxidation reactions. Which one of the following is not an anodic reaction?

A.	Cl- ? Cl+ e-	B.	Fe3+ + e- ? Fe2+
C.	Cu ? Cu2+ + 2e-	D.	Zn ? Zn2+ + 2e-

60.

Which one of the following reactions does not take place at cathode ?

A.	Cl- ? Cl+ e-	B.	H+ + e- ? H
C.	Ag+ + e- ? Ag	D.	Cu2+ +2e- ? Cu