a) Of the following four choices, which is the best reducing agent? i) Ag+ ii) A

Question

a) Of the following four choices, which is the best reducing agent?

i) Ag+ ii) Ag iii) Cu2+ iv) Cu

b) Cars of the future may make use of Hydrogen powered fuel cells. Two possible reactions to consider for this are:

O2 + H2O = OH-

H+ + e- = H2

What would be the voltage E of a fuel cell under the following conditions?

3. (A) Of the following four choices, which is the b h) Ca (B) Cars of the future may make use of hydrogen powered fiuel cells (H powered battery) Twe possible reactions to consider for this are 21r (aq) + 2 e' H, (g) E-0.00V What would be the voltage (E) of a fuel cell under the following conditions? 25 0C H2 gas pressure 1 bar H'1-0.00100 M O, gas pressure I bar [OH'] = 0 0100 M of a fuel cell under the following conditions 2rc

Explanation / Answer

3A.

Here Ag+ is reducing with Electrod potential= +0.80V

While for Cu+2 E = +0.34V

So best reducing agent is Cu+2 ( due to less reduction potential).

B.

Fuel cell reaction is

cathode: O2+ 2H2O + 4e --> 4OH-   E = -0.4

Anode: 2H2 --> 4H+ + 4e        E = 0V

E0 cell = E cathode - Eanode = -0.40 - 0 = -0.40V

E cell = E0cell - 0.0592 log[Anode / cathode] / n

Ecell =-0.40 - 0.0148 log (([H+)4 / (OH-)4 ] = -0.4 - 0.0148 X 4log [ 0.001 / 0.01] = -0.4 + 4 X 0.0148 = -0.3408 V

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