We’re asked to **determine the concentration of I**^{-} if the** cell potential, E _{cell} is zero** and

We will use the** Nernst Equation **which relates the concentrations of compounds and cell potential:

$\overline{){{\mathbf{E}}}_{{\mathbf{cell}}}{\mathbf{=}}{\mathbf{E}}{{\mathbf{\xb0}}}_{{\mathbf{cell}}}{\mathbf{-}}\frac{\mathbf{0}\mathbf{.}\mathbf{592}\mathbf{}\mathbf{V}}{\mathbf{n}}{\mathbf{log}}{\mathbf{}}{\mathbf{Q}}}$

E_{cell} = cell potential under non-standard conditions

E°_{cell} = standard cell potential

n = number of e^{-} transferred

Q= reaction quotient = [products]/[reactants]

In the Nernst Equation, the **E° _{cell} is needed **but only E

We will find Q to **solve for [I ^{-}]** by doing these steps:

*Step 1**. Write the two half-cell reactions and determine the half-cell potentials (refer to the Standard Reduction Potential Table) Step 2. Identify the reduction half-reaction (cathode) and the oxidation half-reaction (anode)Step 3. Get the overall reaction by balancing the number of electrons transferred then adding the reduction half-reaction and oxidation half-reaction.Step 4. Calculate E°_{cell}.*

A voltaic cell is constructed that uses the following half-cell reactions:

l Cu^{+} (aq) + e^{-} → Cu(s)

I_{2} (s) + 2e^{-} → 2I^{-} (aq)

l Cu

I

.

The cell is operated at 298 K with [Cu^{+} ] = 0.26 M and [I^{-} ] = 3.6 M .

If [Cu^{+} ] was equal to 0.16 M , at what concentration of I^{-} would the cell have zero potential?

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