Question

You are tasked to build a voltaic cell with at least a 3v output. In detail explain your voltaic cell; naming each component, describing their function, and provide the complete balance redox reaction

Answer 1

We are tasked to build a voltaic cell which provides atleast a 3 V output. We can fix one of the components, the reducing half as the Cl₂/Cl half cell. The oxidation half can be provided by Na⁺/Na half cell. The standard reduction potentials for the half cells areas below:

Cl₂ (g) + 2 e^- --------> 2 Cl^- (aq); E⁰ = +1.358 V

Na⁺ (aq) + e^- --------> Na (s); E⁰ = -2.714 V

The first equation gives the reduction half. The reduction takes place in the cathode and comprises the cathode half cell. The second reaction gives the reduction of Na⁺; we are however, required to oxidize Na to Na⁺ so that the half cell reaction is reversed (this will also reverse the direction of E⁰). Therefore, the oxidation half (takes place in anode) is given as

Na (s) -------> Na⁺ (aq) + e^-; E⁰ = +2.714 V

Therefore, in the cell comprising of the above two half cells, Na is oxidized to Na⁺ (in the anode) and the electron(s) lost reduce Cl₂ to Cl^- in the cathode. The balanced chemical equation is given as

2 Na (s) + Cl₂ (g) --------> 2 Na⁺ (aq) + 2 Cl^- (aq)

The cell voltage is given by E⁰_cell = E⁰_red + E⁰_ox = (+1.358 V) + (+2.714 V) = +4.072 V, which is higher than the required cell output voltage of +3.00 V.

The cell can be represented as

Pt | Na (s), Na⁺ (aq) || Cl₂ (g), Cl^- (aq) | Pt

Pt provides the solid support for the electrodes.