Question

Suppose you have the following reagents available at$\mathbf{\text{pH}}\mathbf{0}$ , atmospheric pressure, and$1\text{M}$concentration:

${\mathbf{\text{Co}}}_{\mathbf{\left(}\mathbf{s}\mathbf{\right)}}\mathbf{,}{\mathbf{\text{Ag}}}^{\mathbf{+}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{,}{\mathbf{\text{Cl}}}^{\mathbf{-}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{,}{\mathbf{\text{Cr}}}_{\mathbf{\left(}\mathbf{s}\mathbf{\right)}}\mathbf{,}{\mathbf{\text{BrO}}}_{\mathbf{3}}^{\mathbf{-}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{,}{\mathbf{\text{l}}}_{\mathbf{2}}\mathbf{\left(}\mathit{s}\mathbf{\right)}$

a) Which is the strongest oxidizing agent?

b) Which is the strongest reducing agent?

c) Which reagent willreduce${{\mathbf{\text{Pb}}}^{\mathbf{2}\mathbf{+}}}_{\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}}$ whileleaving ${{\mathbf{\text{Cd}}}^{\mathbf{2}\mathbf{+}}}_{\mathbf{\left(}\mathbf{a}\mathbf{q}\mathbf{\right)}}$unreacted?

Short answer

a)${\text{BrO}}_3-$has the most positive standard reduction potential $(+1.52\text{V})$which makes it the strongest oxidizing agent.

b) $\text{Cr}$has the most negative standard reduction potential $(-0.74\text{V})$which makes it the strongest reducing agent.

c)Reagent that will reduce${{\text{Pb}}^{2+}}_{\left(aq\right)}$when${{\text{Cd}}^{2+}}_{\left(aq\right)}$ is left unreacted is Co

Step-by-step solution

Step 1:The cell potential.

The cell potential is the measurement of the potential difference between two half cells in an electrochemical cell.

The strongest oxidizing agent will be the one that has the more positive standard reduction potential.

The strongest reducing agent will be the one that has the more negative standard reduction potential.

Standard reduction potentials for given compounds: 

To solve all subtasks, write standard reduction potentials for given compounds:

$\begin{array}{l}{\text{E}}^{°}({\text{CO}}^{2+}\mid \text{Co})=-0.277\text{V}\\ {\text{E}}^{°}({\text{Ag}}^{+}\mid \text{Ag})=+0.796\text{V}\\ {\text{E}}^{°}({\text{Cl}}_2\mid {\text{Cl}}^{-})=+1.3583\text{V}\\ {\text{E}}^{°}({\text{Cr}}^{3+}\mid \text{Cr})=-0.74\text{V}\\ {\text{E}}^{°}({{\text{BrO}}_3}^{-}\mid {\text{Br}}_2)=+1.52V\\ {\text{E}}^{°}({I_2}^{}\mid I^{-})=+0.535V\end{array}$

Find the strongest oxidizing agent.

a)

The strongest oxidizing agent will be the one that has the more positive standard reduction potential.

Look at the determined standard reduction potentials see that${\text{BrO}}_3-$has the most positive standard reduction potential$(+1.52\text{V})$which makes it the strongest oxidizing agent.

Find the strongest reducing agent. 

b)

The strongest reducing agent will be the one that has the more negative standard reduction potential.

Look at the determined standard reduction potentials see that $\text{Cr}$ has the most negative standard reduction potential $(-0.74\text{V})$ which makes it the strongest reducing agent.

Reagent that will reduce Pb2+(aq)when Cd2+(aq)is left unreacted.

To determine this,

The standard reduction potential for${\text{Pb}}^{2+}\left(aq\right):{\text{E}}^{°}({\text{Pb}}^{2+}\mid \text{Pb})=-0.127\text{V}$

The standard reduction potential for${\text{Cd}}^{2+}\left(aq\right):{\text{E}}^{°}\left({\text{Cd}}^{2+}\text{Cd}\right)=-0.402\text{V}$

Look up and see which compound has the value for standard reduction potential in between those values, andsee that the answer is Co.