A BATTERY. ELECTROCHEMICAL CELLS EXPERIMENT 12 PRE-LABORATORY 1. Last week we wo

Question

A BATTERY. ELECTROCHEMICAL CELLS EXPERIMENT 12 PRE-LABORATORY 1. Last week we worked with an electrochemical cell. This week we are studying voltaic cells Compare and contrast electrolytic d voltaic cells. an 2. Look up the Standard Reduction Potentials (SRPs) for the following half cells 2+ l Fe Ag Fer Sn2+ Sn Pb Pb u24 Cu 3. A student connects a Ni2 (0.5 M)INi(s) half-cel to a Cu2 (1 Micu(s) electrode. When the red lead is attached to the Cu electrode, the cell potential read by the voltmeter, Ear, is +0.60 V. a. What is the reduction half reaction at the cathode (red lead)? b. What is the oxidation half reaction at the anode (black lead)? c. What is the overall cell reaction? d. write the expression for the thermodynamic reaction quotient, Q, and calculate its value for this cell. e. Use the Nernst equation to find the standard cell potential, E ell. Ecell E 0,0257 in Q (at 25 C) f Knowing that the standard reduction potential, E red, of the Cu Cu(s) half cell is +0.34 V, (or knowing that the standard oxidation potential, E of the Cu(s)lcu half cell is -0.34 V), what is the potential of the nickel half-cell? Is this E or Eo g. What is the standard reduction potential (SRP, Eored) of the N 2+ Ni(s) half-cell? (Hint: This is the value from part f with either the same or opposite sign.) 12 I MAKING A BATTERY-ELECTROCHEMICAL CELLS: PRE-LAB 157

Explanation / Answer

3a. cathode: Cu2+ + 2e ------> Cu

3b. anode: Ni ---------> Ni2+ + 2e

3c. Cell reaction: Ni (s) + Cu2+(aq) ---------> Cu (s) + Ni2+(aq)

3d. Q = [Ni2+]/[Cu2+] = 0.5/1 = 0.5

3e. E0cell = E0cathode - E0anode = 0.34 - (-0.25) = 0.59

Ecell = E0cell - (0.0257/n) ln Q = 0.59 - (0.0257/2)(ln 0.5) = 0.59 - (-0.009) = 0.599 V

3f. The potential of nickel half cell is standard oxidation potential . It is E0ox

Ecell = E0red + E0ox

3g.The sandard reduction potentiial of Nickel half cell is - 0.25 V.

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