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41.

In a body-centred cubic lattice system there are

A.	1 atom per unit cell	B.	2 atoms per unit cell
C.	3 atoms per unit cell	D.	4 atoms per unit cell

42.

In a face-centred cubic lattice there are

A.	1 molecule per unit cell	B.	2 molecules per unit cell
C.	4 molecules per unit cell	D.	8 molecules per unit cell

43.

When Fe2+ changes to Fe3+ in a reaction

A.	it loses an electron	B.	it gains an electron
C.	it gains a proton	D.	it loses a proton

44.

A chemical change occurs when iron

A.	rusts	B.	is magnetised
C.	is heated	D.	melts

45.

Which of the following is most readily corroded in air?

A.	Copper	B.	Iron
C.	Tin	D.	Silver

46.

When iron is rusted it is

A.	reduced	B.	decomposed
C.	oxidised	D.	changed in a fine powder

47.

Rust of iron is

A.	powdered iron	B.	ferrous oxide
C.	hydrated ferric oxide	D.	none of the above

48.

Corrosion

A.	involves exchange of electrons in electrochemical corrosion only	B.	involves exchange of electrons in chemical corrosion only
C.	involves exchange of electrons both in electrochemical and chemical corrosion only	D.	is a physical phenomenon

49.

Corrosion is prevented or its rate is reduced by

A.	increasing the resistance between abodic and cathodic area	B.	decreasing anodic or cathodic polarization by increasing the diffusion of reactants and products
C.	decreasing the resistance between anodic and cathodic areas	D.	none of the above

50.

Atmospheric corrosion of metals takes place by

A.	rapid oxidation	B.	slow oxidation
C.	rapdi hydration	D.	none of the above