Chapter 13, Problem 13.90PAE

A chemical engineering student is studying the effect of pH on the corrosion of iron. Ellie following data are collected:

Corrosion Rate (mm/year)	ph
0.03	13.00
0.06	12.00
0.16	11.00
0.22	10.00
0.25	9.00
0.25	8.00
0.25	7.00
0.25	6.00
0.25	5.00
0.27	4.00
0.37	3.00
0.38	2.80
0.63	2.80
1.00	2.80

Plot corrosion rate vs. pH. (HINT: Label the x axis with decreasing pH.)

(a) How would you describe the dependence of corrosion on pH?

(b) When the pH goes below 3, bubbles appear in the solution. What change takes place in the reduction half-reaction at low pH?

(c) How do you explain the shape of the curve at the lowest pH?

(Based on a graph in the Kirk-Otbmer Encyclopedia of Chemical Technology, 4th ed., vol 7. New York: John Wiley & Sons, p. 559.)