Could I get some help with a few electrochemistry problems I\'m struggling with?

Question

Could I get some help with a few electrochemistry problems I'm struggling with? Thanks

Silverware Tamish Low concentrations of hydrogen sulfide in air react with silver to form Ag2S, more familiar to us as tanish. Silver polish contains aluminum metal powder in an alkaline suspension. a. Write a balanced net ionic equation for the redox reaction of Ag2S and Al metal that produces Ag metal and Al(OH)3. Be sure to include phases for each species in the equation. Tip: Plus signs (+) can be typed from the keyboard. Reaction arrows can be found in the Tools menu of the answer module. Include phases in the balanced chemical equation. Click on the (aq) button in the tools to select the phase to add. Phases should not be subscripted b. Calculate E° for the reaction in Part a. [Hint: Derive E values for the half-reactions in which Ag2S is reduced to Ag metal and Al(OH)3 is reduced to Al metal. You can do this by combining the standard potentials for the reduction of Ag and Al3* in Appendix 6 with the Ksp expressions and values of Ag2S (Kap 1.6x10-49) and Al(OH)s (Ksp -1.9 x10-3) Number

Explanation / Answer

1) anode half reaction:-

Ni(s) ------> Ni2+(aq) + 2e-

cathode half reaction :-

Ag+(aq) + e- -------> Ag(s)

Overall balanced reaction:-

2Ag+(aq) + Ni(s) ----> 2Ag(s) + Ni2+(aq)

2) 5Fe2+(aq) + MnO4-(aq) + 8H+(aq) -----> 5Fe3+(aq) + Mn2+(aq) + 4H2O(l) ; Ecell = 1.49 - (-0.77) = 2.26 V

Thus, n*F*E = R*T*lnKeq

or, 5*96500*2.26 = 8.314*298*lnK

or, lnK = 440.128

or,K = 1.4*10191

3) delta G = -n*F*E = -2*96500*2 = -386000 J = -386 kJ

4) Anode material = Cd

Equivalent mass of Cd = molar mass/2 = 112.4/2 = 66.2 g/equivalent

Now, as per Faraday's Law, 96500 C is required per equivalent of a compound

Thus, per gram of Cd, charge required = 96500/66.2 = 1457.7 C/g

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---