Industrially, sodium metal is obtained by electrolyzing molten sodium chloride. The reaction at the cathode is \(\mathrm{Na}^{+}+e^{-} \longrightarrow \mathrm{Na}\). We might expect that potassium metal would also be prepared by electrolyzing molten potassium chloride. However, potassium metal is soluble in molten potassium chloride and therefore is hard to recover. Furthermore, potassium vaporizes readily at the operating temperature, creating hazardous conditions. Instead, potassium is prepared by the distillation of molten potassium chloride in the presence of sodium vapor at \(892^{\circ} \mathrm{C}\) : $$\mathrm{Na}(g)+\mathrm{KCl}(l) \rightleftharpoons \mathrm{NaCl}(l)+\mathrm{K}(g)$$ In view of the fact that potassium is a stronger reducing agent than sodium, explain why this approach works. (The boiling points of sodium and potassium are \(892^{\circ} \mathrm{C}\) and \(770^{\circ} \mathrm{C},\) respectively. \()\)

Step by step solution

01

Understand the Reactions

The key to answering this question is understanding that potassium is a stronger reducing agent than sodium. As a reducing agent, potassium has a higher tendency than sodium to lose electrons. This tendency is replicated in the reaction where the sodium atom displaces the potassium from the molten potassium chloride.

02

Comprehend the Reaction Conditions

Notice that the reaction is conducted at \(892^{\circ} \mathrm{C}\), which is the boiling point of sodium but above the boiling point of potassium. Thus, while the sodium is in a gaseous state, the potassium is also likely vaporizing due to its lower boiling point.

03

Explain the Reaction

This reaction works because the reducing ability of potassium allows it to give up its electron more readily than sodium. Thus, a sodium atom can replace a potassium ion from the molten potassium chloride forming sodium chloride, while simultaneously releasing potassium in a gaseous state. By conducting the reaction at these temperatures, the gaseous potassium can be easily collected, despite its solubility in molten potassium chloride and tendency to vaporize.

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