Question

We know that an electrolytic cell has three main components, an electrolyte and two electrodes (an anode and a cathode) and the electrolyte can come in two forms, either as molten or in an aqueous solution. Which of the following statements accurately describes an electrolytic cell?

• A. Alkali or alkaline earth metals, which are the cations of the electrolyte, do not get oxidized in an aqueous solution since water is more easily oxidized.
• B. Polyatomic ions, which are the anions of the electrolyte, are typically more easily oxidized than water.
• C. In both molten or aqueous forms, the cation will be reduced and the anion will be oxidized.
• D. For aqueous solutions of the electrolyte, a gas may be produced at the anode.

Answer 1

The correct option is D For aqueous solutions of the electrolyte, a gas may be produced at the anode.

Before starting, let us first establish some facts.
In an aqueous electrolyte, it is highly likely that water is more easily reduced since water has lower oxidation potential than most alkali and alkaline earth metals. Remember the electrochemical series? The alkali metals have a positive oxidation potential. $H^{+}$ in water has 0.
Also, most polyatomic anions, like Sulphate, won’t get more easily oxidized than water.

Now, let’s look at these statements one by one and try to eliminate.

Statement A is almost true, but the word should have been reduced instead of oxidized.

Statement B is false, since we saw that polyatomic anions are less easily oxidized as compared to water.

Statement C is false since in the aqueous form but true in the molten form, since in the aqueous water may also get oxidized or reduced.

Statement D is right, since the word is may. A gas may be produced, which is $H_2$, if the $H^{+}$ in water gets reduced to $H_2$ since water has lower oxidation potential or higher reduction potential than most alkali and alkaline earth metals which are most commonly used cations.