Question

What reaction will take place at the cathode and the anode when each of the following is electrolyzed?
a. molten KF b. molten CuCl₂c. molten MgI₂

Short answer

The reaction can be found when it is electrolyzed.

Step-by-step solution

Reaction when it is electrolyzed with molten KF

Molten KF has two elements: fluorine and potassium. Reaction of reduction for potassium can be denoted as:

$K^{+}+e^{-}\to K$

Reduction potential is -2.92 V.

Reaction of reduction for fluorine can be denoted as:

$F_2+2e^{-}\to 2F^{-}$

Reduction potential is 2.87 V. The reduction potential of fluorine is higher than potassium so that the reaction is reduced at cathode. The reduction at cathode and anode can be denoted as:

$$\begin{gathered} Cathode: K^{+}+e^{-}\to K \\ Anode: 2F^{-}\to F_2+2e^{-} \end{gathered}$$

Reaction when it is electrolyzed with molten CuCl2

Molten CuCl₂ has two elements: copper and chlorine. Reaction of reduction for copper can be denoted as:

$C{u}^{2+}+2e^{-}\to Cu$

Reduction potential is 0.34 V.

Reaction of reduction for chlorine can be denoted as:

$C{l}_2+2e^{-}\to 2C{l}^{-}$

Reduction potential is 1.36 V. The reduction potential of chlorine is higher than copper so that the reaction are reduced at cathode.

The reduction at cathode and anode can be denoted as:

$$\begin{gathered} Cathode: C{u}^{2+}+2e^{-}\to Cu \\ Anode:C{l}_2+2e^{-}\to 2C{l}^{-} \end{gathered}$$

Reaction when it is electrolyzed with molten MgI2

Molten MgI₂ has two elements: magnesium and iodine. Reaction of reduction for magnesium can be denoted as:

$M{g}^{2+}+2e^{-}\to Mg$

Reduction potential is -2.37 V.

The reaction of reduction for iodine can be denoted as:

$I_2+2e^{-}\to 2I^{-}$

Reduction potential is 0.54 V. The reduction potential of iodine is higher than magnesium so that the reaction is reduced at cathode. The reduction at cathode and anode can be denoted as:

$$\begin{gathered} Cathode: M{g}^{2+}+2e^{-}\to Mg \\ Anode:2l^{-}\to l_2+2e^{-} \end{gathered}$$