Chapter 19, Problem 19.18A

Accidentally chewing on a stray fragment of aluminum foil can cause a sharp tooth pain if the aluminum comes in contact with an amalgam filling. The filling, an alloy of silver, tin, and mercury, acts as the cathode of a tiny galvanic cell, the aluminum behaves as the anode, and saliva serves as the electrolyte. When the aluminum and the filling come in contact, an electric current passes from the aluminum to the filling, which is sensed by a nerve in the tooth. Aluminum is oxidized at the anode, and 0₂ gas is reduced to water at the cathode.
(a) Write balanced equations for the anode, cathode, and overall cell reactions.
(b) Write the Nernst equation in a form that applies at body temperature 37 °C.
(c) Calculate the cell voltage at 37 °C. You may assume that $[A{l}^{3+}]=1.0\times {10}^{-9}$
$M,P{o}_2=0.20\text{ atm}$ ,and that saliva has a pH of 7.0. Also assume that the E° values in Table 19.1 apply at 37 °C.