2Al(s) + 3Mn2+(aq) 2Al3+(aq) + 3Mn(s) = E°cell → predict whether is larger or smaller than for the following cases. Ecell E°cell a. [Al3+ ] = 2.0 [Mn2+ ] = 1.0 M, M b. [Al3+ ] = 1.0 [Mn2+] = 3.0 M, M A: < B: > For a more quantitative approach….. When cell is not at standard conditions, use Nernst Equation: = Gas constant 8.315 J/K mol R = Faraday constant F = reaction quotient [products] coefficient/[reactants] coefficient Q = Energy produced by reaction E = Temperature in Kelvins T = # of electrons exchanged in BALANCED redox equation n Rearranged, another useful form NERNST EQUATION: @ 25C (298K) As declines with reactants converting to products, eventually reaches zero. E E Zero potential means reaction is at equilibrium [dead battery]. Also, AND = 0 as well. Q = K ΔG CONCENTRATION CELLS We can construct a cell where both compartments contain the same components BUT at different concentrations Notice the difference in the concentrations pictured at left. Because the right compartment contains 1.0 M Ag+ and the left compartment contains 0.10 Ag+, there will be a driving force to transfer electrons from M left to right. Silver will be deposited on the right electrode, thus lowering the concentration of Ag+ in the right compartment. In the left compartment the silver electrode dissolves [producing Ag+ ions] to raise the concentration of Ag+ in solution. Exercise 6 Determine the direction of electron flow and designate the anode and cathode for the cell represented here.
2Al(s) + 3Mn2+(aq) → 2Al3+(aq) + 3Mn(s) E°cell = predict whether Ecell is larger or smaller than E°cell for the following cases. a. [Al3+ ] = 2.0 M, [Mn2+ ] = 1.0 M b. [Al3+ ] = 1.0 M, [Mn2+] = 3.0 M A: < B: > For a more quantitative approach….. When cell is not at standard conditions, use Nernst Equation: R = Gas constant 8.315 J/K mol F = Faraday constant Q = reaction quotient [products] coefficient/[reactants] coefficient E = Energy produced by reaction T = Temperature in Kelvins n = # of electrons exchanged in BALANCED redox equation Rearranged, another useful form NERNST EQUATION: @ 25C (298K) As E declines with reactants converting to products, E eventually reaches zero. Zero potential means reaction is at equilibrium [dead battery]. Also, Q = K AND ΔG = 0 as well. CONCENTRATION CELLS We can construct a cell where both compartments contain the same components BUT at different concentrations Notice the difference in the concentrations pictured at left. Because the right compartment contains 1.0 M Ag+ and the left compartment contains 0.10 M Ag+, there will be a driving force to transfer electrons from left to right. Silver will be deposited on the right electrode, thus lowering the concentration of Ag+ in the right compartment. In the left compartment the silver electrode dissolves [producing Ag+ ions] to raise the concentration of Ag+ in solution. Exercise 6 Determine the direction of electron flow and designate the anode and cathode for the cell represented here.
17%20Electrochemistry%20modified.docx