**Correct Option: C. Oxygen at the Anode and Hydrogen at the Cathode** ### Explanation of the Correct Answer In the electrolysis of dilute sulfuric acid (H₂SO₄) using platinum electrodes, we are essentially breaking down the acid into its constituent ions and then using an electric current to drive the reaction. 1. **Understanding Electrolysis**: - Electrolysis is a process that uses electricity to cause a chemical change, typically to decompose a compound into its elements or simpler compounds. - In this case, sulfuric acid dissociates in water to form hydrogen ions (H⁺) and sulfate ions (SO₄²⁻). 2. **Electrode Reactions**: - **At the Cathode (Negative Electrode)**: - The cathode attracts cations (positively charged ions). In dilute sulfuric acid, the primary cation is the hydrogen ion (H⁺). - The reduction reaction occurring at the cathode can be represented as: \[ 2H^+ + 2e^- \rightarrow H_2(g) \] - This means that hydrogen gas (H₂) is produced at the cathode. - **At the Anode (Positive Electrode)**: - The anode attracts anions (negatively charged ions). In dilute sulfuric acid, the primary anion is the sulfate ion (SO₄²⁻), but water (H₂O) is also present and can participate in the reaction. - The oxidation reaction occurring at the anode can be represented as: \[ 2H_2O \rightarrow O_2(g) + 4H^+ + 4e^- \] - This means that oxygen gas (O₂) is produced at the anode. ### Why Other Options Are Incorrect - **Option A: Sulphur and Hydrogen**: - This option is incorrect because sulfur is not produced during the electrolysis of sulfuric acid. The electrolysis primarily involves the decomposition of water and the ions present in the acid, leading to the production of hydrogen and oxygen gases. - **Option B: Hydrogen and Oxygen**: - While hydrogen and oxygen are indeed produced, this option does not specify which gas is produced at which electrode. It is essential to identify that hydrogen is produced at the cathode and oxygen at the anode. Therefore, this option is too vague and does not accurately reflect the electrolysis process. - **Option D: Hydrogen Sulfate Ions**: - This option is incorrect because hydrogen sulfate ions (HSO₄⁻) are not the products of electrolysis. Instead, the electrolysis of sulfuric acid leads to the production of hydrogen gas at the cathode and oxygen gas at the anode, not any ions. ### Summary of Key Points - **Electrolysis of Dilute Sulfuric Acid**: Involves the breakdown of H₂SO₄ into H⁺ and SO₄²⁻ ions. - **Products at Electrodes**: - **Anode**: Oxygen gas (O₂) is produced through the oxidation of water. - **Cathode**: Hydrogen gas (H₂) is produced through the reduction of hydrogen ions. - **Electrode Reactions**: - Cathode: \(2H^+ + 2e^- \rightarrow H_2(g)\) - Anode: \(2H_2O \rightarrow O_2(g) + 4H^+ + 4e^-\) ### Revision Summary - Electrolysis of dilute sulfuric acid produces hydrogen at the cathode and oxygen at the anode. - The reactions involve the reduction of hydrogen ions and the oxidation of water. - Understanding the roles of the electrodes is crucial for predicting the products of electrolysis. - Remember that sulfur is not a product of this reaction, and be cautious of vague options that do not specify the electrode reactions.