37) Metals whose standard reduction potentials that are more positive than that

Question

37) Metals whose standard reduction potentials that are more positive than that of oxygen reacting with protons and electrons to afford water (1.23 V) are?

a) prone to rapidly oxidize in air

b) will not oxidize in air

c) will oxidize only if water is present

d) are already oxidized

.

38) Semiconductors are p-doped by adding ?

a) phosphorus , P.

b) urine

c) boron

d) germanium arsenide

.

39) Semiconductors are n-doped by adding ?

a) phosphorus , P.

b) urine

c) boron

d) germanium arsenide

.

40) Malleable iron is ?

a) wrought iron with cementite crystals

b) wrought iron with rosettes of graphite

c) pure ferrite

d) ferrite with cementite islands

Please answer all of them without guessing!!! Thanks

Explanation / Answer

37) Metals whose standard reduction potentials that are more positive than that of oxygen reacting with protons and electrons to afford water (1.23 V) are,

d) are already oxidized

higher the +ve electrode potential, stronger is the oxidizing agent.

38) Semiconductors are p-doped by adding,

c) boron

Group III elements are good for p-doping

39) Semiconductors are n-doped by adding,

a) phosphorus , P.

Pentavalent elements are the choise for making an n-type doped semiconductor

40) Malleable iron is,

a) wrought iron with cementite crystals

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