Electrolysis of Aqueous Solutions Flashcards

All 7 cards in this deck

What are the steps to predict the products of electrolysis of an aqueous solution of one ionic compound?
e.g. sodium chloride solution

1. Cathode: hydrogen if the metal is more reactive than hydrogen, otherwise the metal — sodium is more reactive, so hydrogen.
2. Anode: the halogen if halide ions are present, otherwise oxygen — chloride ions are present, so chlorine.

Which two ions from water are present in every aqueous solution being electrolysed?

Hydrogen ions ($\mathrm{H^+}$) and hydroxide ions ($\mathrm{OH^-}$), made when water molecules break down.

What is seen at each electrode when copper sulfate solution is electrolysed with inert electrodes?

A pink-brown coating of copper on the negative electrode and bubbles of oxygen gas at the positive electrode.

Why does the blue colour of copper sulfate solution fade during electrolysis?

The copper ions are discharged (removed from the solution), so the solution becomes less concentrated.

True or false? When potassium iodide solution is electrolysed, potassium is produced at the negative electrode.

False. Hydrogen is produced, because potassium is more reactive than hydrogen.

Name the alkaline solution left behind when sodium chloride solution is electrolysed.

Sodium hydroxide ($\mathrm{NaOH}$).

True or false? When sodium sulfate solution is electrolysed using inert electrodes, hydrogen is produced at the negative electrode.

True. Sodium is more reactive than hydrogen, so hydrogen is discharged instead of the metal.