AP Chemistry Chapter 20 ElectrochemistryGalvanic Cells

AP Chemistry Chapter 20 ElectrochemistryGalvanic Cells Key

1. Explain the difference between a galvanic and electrolytic cell.Galvanic cells will have a spontaneous reaction occur, producing electric current.

Electrolytic cells have electricity used to force a reaction to occur that is not spontaneous.2. Why is it necessary to use a salt bridge or a porous disk in a galvanic cell?The salt bridge completes the electrical circuit and allows counter ions to flow into the two cell compartments to maintain electrical neutrality. It also separates the cathode and anode compartments such that electrical energy can be extracted. If the cathode and anode compartments are not separated, the cell would rapidly go to equilibrium without any useful work being done.3. Define the following:

(a) cathodeelectrode at which reduction occurs.(b) anodeelectrode at which oxidation occurs.(c) oxidation half-reactionHalf-reaction in which electrons are products.(d) reduction half-reactionHalf-reactions in which electrons are reactants.3. Sketch the galvanic cells based on the following overall reactions. Show the direction of the electron flow, the direction of the ion migration through the porous disk, and identify the cathode and the anode. Give the overall balanced reaction. Assume that all concentrations are 1.0 M and that all partial pressures are 1.0 atm.

(a) Cr3+(aq) + Cl2(g) Cr2O(aq) + Cl(aq)No solids in the reaction, sooooo we need another type of electrode that is nonreactive such as platinum, gold or graphite.(b) Cu2+ (aq) + Mg(s) Mg2+ (aq) + Cu(s)

(c) IO(aq) + Fe2+(aq) Fe3+(aq) + I2(s)

(d) Zn(s) + Ag+(aq) Zn2+(aq) + Ag(s)4. Sketch the diagram for galvanic cells (standard conditions) utilizing the following half-cells. Write the balanced equations for the overall cell reaction.

(a)

Cathode Anode

a. Cl2/Cl Br/Br2b. IO/ IO Mn2+/MnO

(b) Cathode Anode

a. Ni2+/Ni Al/Al3+b. Co2+/ Co3+ Fe3+/ Fe2+

5. Give the standard line notation for each cell in problems 3 and 4.

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