For the following electrochemical cell: Cu(s)/Cu 2+ (aq, 0.0155 M)//Ag + (aq, 2.
ID: 991241 • Letter: F
Question
For the following electrochemical cell: Cu(s)/Cu2+(aq, 0.0155 M)//Ag+(aq, 2.50 M)/Ag(s)
write the net cell equation. Phases are optional. Do not include the concentrations. Calculate the following values at 25.0 degrees C using standard potentials as needed: Eknot cell (V), Delta Gknot reaction (kJ/mol), E cell (V), Delta G reaction (kJ/mol).
Ok so this is a question on my sapling homework and I entered:
Cu + 2Ag+ -> Cu2+ +2Ag (correct)
Eknot cell = Eknot red + Eknot ox: (0.80) + (-0.34) = 0.46 V (correct)
*Delta Gknot rxn = nFEknotcell: -2(96,485)(0.46) = -88766.2 J = -8877 kJ/mol (incorrect)
Delta G rxn = Delta Gknot rxn + RTln(Q): -88.77 + (8.3145 x 10-3)(298)[ln(0.155/(2.50)2)] = -103.69 kJ/mol (correct)
*E cell = (-Delta G rxn)/(nF): (-103.690)/[(2)(96485)] = 0.54 V or 0.5 V (incorrect)
Explanation / Answer
Cu (s)/Cu +2 (aq, 0.0155 M)// Ag+ (aq, 2.50 M)/ Ag (s)
Cu + 2Ag+ Cu+2 + 2Ag
E o cell = E o reduction + E o oxidation
= 0.80 + (-0.34) = 0.46 V
G orxn =- nF E o cell
= - 2 X 96485 X 0.46
= -88766.2 J / -88.77 Kj/mol
G orxn = G orxn + RTln Q
= -88.77 + (8.314 X 10-3) ln 0.155/2.50
= -103.69 Kj/mol
E cell = -G orxn /nF
= -103.69/2 X 96485
= -0.54 V
E cell = E o cell-0.059 V/n log Q
= 0.46-0.059/2 log 0.0155/2.50
= -1.76 V
G = -nFE cell
= - 2 X 96485 X -1.76
= 339627.2 J/mol / 339.6 Kj/mol