Using the Pourbaix diagram (below): (a) What is the chemical form of iron that i

Question

Using the Pourbaix diagram (below):

(a) What is the chemical form of iron that is the strongest oxidizing agent?

(b) What form of iron is the strongest reducing agent?

(c) What form of iron would predominate in a neutral solution at a potential of 0.00V?

(d) What is the standard reduction potential for FeO4 2- being reduced to Fe3+?

(e) What is the standard reduction potential for Fe2+being reduced to Fe metal?

(f) At what acid/base condition(s) will Fe metal most vigorously reduce water?

Explanation / Answer

a)

For the strongest OXIDIZING AGENT; that is, the most reductive material, i.e. will most likely get those electrons in solution:

Must be Fe+3, since it will "strip" electrons easily than Fe+2 and Fe0

b)

strongest reducing agnet = the most oxidative material, form a), then choose FeO42-

c)

in neutral solution, and Ev = 0... then

pH neutral = 7

y-axis = 0 and pH = 7 so:

Fe+2 in solution is most likely to be present and stable

d)

the redution potential betwen FeO4-2 and fE+3:

standard means pH = 7 by definition so:

eV = between 1.4 and 2.0 eV

e)

Fe and Fe+2, also at pH = 7

should be eV = -0.45 approx (between -0.4 and 0.8)

f)

Fe most likely to reduce water...

at high pH sincce Fe(OH)2 is strongly favoured

pH > 10

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