Accidentally chewing on a stray fragment of aluminum foil can cause a sharp toot
ID: 1066083 • Letter: A
Question
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 O2 gas is reduced to water at the cathode. Calculate the cell voltage at 37C. You may assume that [Al3+] = 1.3×109 M , PO2 = 0.19 atm , and that saliva has a pH of 7.0. Also assume that the E values in Appendix D in the textbook apply at 37 C. E=E2.303RT/nFlog [Al3+]4/(PO2)3[H+]12 PLEASE SHOW ALL STEPS! Thank you for the help.
Explanation / Answer
Al(s) -->
O2(g) + 4 H+ + 4 e 2 H2O +1.229
Al3+ + 3 e Al(s) 1.662
Aluminium must be inverted
Al(s) Al3+ + 3 e +1.662
E°cell = Ered - EOx = 1.229+1.662 = 2.89
E=E2.303RT/nF*log ([Al+3]^4 / [P-O2]^3[H+]^12)
E=2.892.303*8.314*(37+263)/(12*96500)*log ((1.3*10^-9)^4 / ((0.19^2)(10^-7)^2)
E = 2.98971 V