Question

Construct a cell using standard hydrogen electrode and zinc electrode. Write its cell reaction and cell representation. Calculate cell potential of a cell with 0.01 M Zn²⁺ ions. Standard potential of a cell is +0.76 V.

Answer 1

Cell Reaction:

1. At the anode (zinc electrode), oxidation occurs:
   \[\ce{Zn_{(s)} -> Zn^2+_{ (aq)} + 2e^-}\]
2. At the cathode (SHE), reduction occurs:
   \[\ce{2H^+_{ (aq)} + 2 e^- -> H_2_{(g)}}\]
3. Overall Cell Reaction:
   \[\ce{Zn_{(s)} + 2H^+_{ (aq)} -> Zn^2+_{ (aq)} + H2_{(g)}}\]

Cell representation:

\[\ce{Zn_{(s)} | Zn^2+_{ (aq)} (0.01 M) || H^+_{ (aq)} (1 M) | H_2_{(g)} | Pt_{(s)}}\]

Given:

[Zn²⁺] = 0.01 M

`E_(Zn)^0` = +0.76V

[H⁺] = 1 M

n = 2

To find:

E_Zn = ?

Calculation:

`E_(cell) = E_(cell)^0 - 0.0592/n log_10  [[Zn^(2+)]]/[H^+]^2`

= `0.76 - (0.0592)/n log_10  0.01/1^2`

= `0.76 - 0.0592/2 xx (-2)`  ...[log₁₀ (0.01) = −2]

= 0.76 + 0.0592

= 0.8192 V