BridgeRedox and electrochemistryFree

A zinc–silver cell and dichromate oxidations

Galvanic cells, E°cell, salt bridges, balancing redox equations

E°

(V):

\ce{Zn^2+/Zn}

−0.76;

\ce{Cu^2+/Cu}

+0.34;

\ce{I2/I-}

+0.54;

\ce{Ag+/Ag}

+0.80;

\ce{Cr2O7^2-/Cr^3+}

+1.33. A cell is built from a zinc electrode in

\ce{Zn(NO3)2(aq)}

and a silver electrode in

\ce{AgNO3(aq)}

, joined by a

\ce{KNO3}

salt bridge.

Facts you may need

Write the half-equations and overall equation, identify the anode and cathode, give the direction of electron flow, and calculate

E°_{cell}

Describe what would be observed at each electrode as the cell operates. Explain the role of the salt bridge and why KCl would not be suitable.

Acidified dichromate oxidises iodide ions. Write the balanced equation, calculate

E°_{cell}

, and describe the observations.

A student suggests that silver metal could be used to remove

\ce{Cu^2+}

ions from waste water. Use

E°

values to evaluate this suggestion.