a. Will iron nails rust when it is exposed to pure water (pH = 7). Support your

Question

a. Will iron nails rust when it is exposed to pure water (pH = 7). Support your answer with calculation and data found in the standard potential table. Write down the oxidation and reduction reactions for the spontations system. b. When an iron pipe is exposed to acid rain with a pH of 4 and oxygen dissolving in the water. Assume the partial pressure of O_2 in air is 0.2 atm. What is the reduction potential for the half reaction: c. Based on the result in (b), will the oxidation of iron from Fe to Fe^2+ be thermodynamically spontaneous Explain your answer and show your calculations d. Which of the following metals, if coated onto iron, would prevent the corrosion of iron? Zn, Sn, Co How would it prevent the corrosion of iron? Support your answer with calculations.

Explanation / Answer

Q1a

Most likely, since water ad oxygen are present

O2(g) + 2H2O + 4e– 4OH–(aq) +0.401

and iron has a lower potential:

Fe3+(aq) + 3e– Fe(s) -0.04

oxidatoin reaction:

Fe(s)Fe3+(aq) + 3e–

So expect Fe(s) --> Fe+3(q)

E°= Ered - Eox = 0.401 - -0.04 = 0.441 V, positive meaning it is spontaneous

b)

pH = 4, O2 in water

P-O2 = 0.2 atm

find the potential

reduciton half reaction

O2(g) + 2H2O + 4e– 4OH–(aq) +0.401

[OH-] = 10^-(14-4) = 10^-10

Q = [OH-]^4 / P-O2

E° = 0.401 - 0.0592/4 * log((10^-10)^4 / 0.20 )

E° = 0.982655 V

c)

once again, since °E > Eiron

this is very likely to be spontaneous

d)

prevnesion of corrosion

Zinc, has lower potential, therefore oxidizes fist, AND helps to build a protective coat over the iron pipe

E° > E°

Zn2+(aq) + 2e– Zn(s) –0.76

Ezn< Efe

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.