The cell diagram for the lead-add cell that is used in automobile and truck batt

Question

The cell diagram for the lead-add cell that is used in automobile and truck batteries is Pb(s)PbSO_4(s)H_2SO_4(aq)|PbO_2(s), PbSO_4(s)Pb(s) where the comma between PbO_2(s) and PbSO_4(s) denotes a heterogeneous mixture of the two solid and the right-hand lead electrode is nonreactive. (a) Write the balanced equation for the net cell reaction (b) Look up standard potentials for the oxidation and the reduction reactions, then calculate the value of E_cell. (c) Calculate the value of Delta G^4_cm (d) Calculate the value of E_cell at 25 degree C If (H_2SO_4) = 10 0 M (e) How many lead-acid cells are in a 12 V car battery?

Explanation / Answer

(a)
Pb(s)+SO4(2-) (aq) --> PbSO4(s) + 2e-
PbO2(s) + SO4(2-) (aq) + 4H+ (aq) + 2e- --> PbSO4 (s) + 2H2O (l)
net rxn: Pb(s)+PbO2(s)+2SO4(2-) (aq) + 4H+ --> 2PbSO4 (s) + 2H2O (l)

(b)
1.6913V - (-0.3588V)= 2.0501V = 2.05 V
(You can look at which voltages are which in the standard potential table)

(c) I used the deltaG= -nFE(cell) equation
deltaG= -(2)(96.485 kJ/V x mol)(2.05V)
= -395.58 kJ/mol

(d) There are three variations of this equation but i used this one
Ecell= Ecell(standard)- (0.0592V/n)(logQ)
Ecell= 2.05 V- (0.0592/2)(log(10))
=2.02 V

(e)
I googled this part and it usually has 6 cells in a 12 V car battery

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