The occurrence of anodic and cathodic sites on the same surface can be demonstrated by the

following experiment $[17].$ In a small petri dish containing a $3\%$ NaCl solution, immerse a plain

iron nail which has been thoroughly cleaned with abrasive paper just prior to its immersion.

Add $5ml$ of $5\%$ potassium ferricyanide solution and $1ml$ of a $1\%$ phenolphthalein solution

in alcohol. When anodic areas develop on the nail, they will appear as a blue color. The blue

color reveals the presence of ferrous ions. Cathodic areas which produce hydroxyl ions, as per

Eq$.(7),$ will give a red color in the presence of the acid$-$base indicator phenolphthalein.

$($a$)$ On what part of the nail do the anodic areas appear? Explain why they appear at that

location.

$($b$)$ Suppose that the nail is bent in half before immersion. Would the bent part of the nail

produce anodic or cathodic regions? Explain your answer.