Question

A solution of potassium sulphate in water is electrolysed using inert electrodes. The products at the cathode and anode are respectively. (a) \(\mathrm{H}_{2}, \mathrm{O}_{2}\) (b) \(\mathrm{O}_{2}{ }^{\circ} \mathrm{H}_{2}\) (c) \(\mathrm{O}_{2}, \mathrm{Na}\) (d) None of these

Short answer

The products of electrolysis of potassium sulphate in water with inert electrodes are H2 at the cathode and O2 at the anode, so the correct answer is (a).

Step-by-step solution

Identify the Electrolysis Process

Electrolysis of a solution involves the breakdown of the solvent and its dissolved compounds by electric current. The electrodes used do not participate in the reaction if they are inert.

Determine Products at the Cathode

At the cathode, cations migrate and are reduced. In a water solution electrolysis, water can be reduced to hydrogen gas, given as H2, if no other cation is more easily reduced.

Determine Products at the Anode

At the anode, anions migrate and are oxidized. Sulfate ions are difficult to oxidize, so the water is likely to give up electrons to form oxygen gas, given as O2.

Choose the Correct Answer

The correct answer is the one that lists hydrogen gas as the product at the cathode and oxygen gas as the product at the anode. Therefore, the correct answer is (a) H2 at the cathode and O2 at the anode.

Key concepts

Electrochemistry

Electrochemistry is a branch of chemistry that deals with the chemical action of electricity and the production of electricity by chemical reactions. In a typical electrochemical process, electrolysis, an electrical current is passed through a substance to effect a chemical change. This process is harnessed in a variety of applications, including recharging batteries, electroplating metals, and decomposing chemical compounds.

Electrolysis involves two electrodes: an anode (positive charge) and a cathode (negative charge). When an electrolyte solution, such as potassium sulphate dissolved in water, is subjected to an electric current, positive ions (cations) move to the cathode to gain electrons (reduction), while negative ions (anions) move to the anode to lose electrons (oxidation). The substances produced at each electrode during electrolysis depend on the nature of the material being electrolyzed and the type of ions present in the solution.

Inert Electrodes in Electrolysis

Inert electrodes are crucial in the process of electrolysis as they do not actively participate in the chemical reactions occurring at the electrode surfaces. They provide a surface for the electrolysis reactions to occur but are not consumed or altered during the process. Inert electrodes are typically made from materials such as platinum, graphite, or other substances that have high stability under the electrolysis conditions.

In the electrolysis of potassium sulphate, inert electrodes serve as the conduit for the electrical current that drives the electrolysis. They ensure that the electrolytic reactions are limited to the interaction between the water and potassium sulphate ions. The use of inert electrodes is important for accurately determining the products of electrolysis, as they do not introduce additional reactions or products into the system.

Products of Electrolysis

The products of electrolysis are the substances formed at the electrodes during the electrolysis process. These products result from the reduction of cations at the cathode and the oxidation of anions at the anode. In the case of potassium sulphate electrolysis, the primary components in the solution are water (H₂O) and potassium sulphate (K₂SO₄).

At the cathode, the reduction of water molecules leads to the production of hydrogen gas (H₂). At the anode, the oxidation of water, rather than sulfate ions (which are difficult to oxidize), leads to the formation of oxygen gas (O₂). Despite potassium ions being present, they are not readily reduced in the presence of water, as water has a lower reduction potential. Therefore, the correct products of electrolysis for this solution, using inert electrodes, are hydrogen gas at the cathode and oxygen gas at the anode, in line with option (a) from the exercise provided.