Question

What is the overall cell potential for this redox reaction? Cd + Hg22+ → Cd2+ + 2Hg Given: Cd2+ + 2e− → Cd(s) = –0.40 and Hg22+ + 2e− → 2Hg(l) = 0.79 –0.19 V 0.19 V 0.91 V 1.19 V

Answer 1

The overall cell potential for this redox reaction : 1.19V

Cd + Hg₂²⁺ → Cd²⁺ + 2Hg

Further explanation

Cell potential (E °) is the potential difference between the two electrodes in an electrochemical cell.

Electric current moves from a high potential pole to a low potential, so the cell potential is the difference between an electrode that has a high electrode potential (cathode) and an electrode that has a low electrode potential (anode)

$\large{\boxed {\bold{E ^osel = E ^ocatode -E ^oanode}}}$

or:

E ° cell = E ° reduction-E ° oxidation

(At the cathode the reduction reaction occurs, the anode oxidation reaction occurs)

The value of E⁰ cells uses a reference electrode which is used as a comparison called the Standard Electrode which is the hydrogen-platinum electrode

In reaction:

Cd + Hg₂²⁺ → Cd²⁺ + 2Hg

Given:

Cd²⁺+ 2e⁻ → Cd (s) = –0.40V and

Hg²⁺ + 2e⁻ → 2Hg (l) = 0.79V

From the value of E ° cells, it can be seen that the higher E ° cells will act as positive poles or cathodes namely Hg₂²⁺

So the reaction happens

at the anode (oxidation reaction) Cd ------> Cd²⁺ + 2e⁻ E ° = +0.40 V

at the cathode (reduction reaction) Hg₂²⁺ + 2e− → 2Hg (l) = 0.79 V

E ° cell = E ° cathode -E ° anode = 0.79 V - (-0.40V) = 1.19V

Learn more

The standard cell potential

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Keywords: cell potential, cathode, anode, reduction, oxidation

Answer 2

Answer:  1.19 V

Explanation:

Standard potential for an electrochemical cell is given by:

$E^0{cell}$ = standard electrode potential =$E^0{cathode}-E^0{anode}$

The $E^0$ values have to be reduction potentials.  

Given:

$E^o_{Cd^{2+}/Cd}=-0.40V$

$E^o_{Hg_2^{2+}/Hg}=0.79V$

$Cd+Hg_2^{2+}\rightarrow Cd^{2+}+2Hg$

Cadmium is losing electrons , undergo oxidation and thus act as anode. mercury is gaining electrons, undergo reduction and thus acts as cathode.

$E^0{cell}$ = standard electrode potential =$E^0{cathode}-E^0{anode}=0.79-(-0.40)=1.19V$

Thus the standard potential for an electrochemical cell with the cell reaction is 1.19 V.