(b) Write the half-reaction that occurs at a hydrogen electrode in acidic aqueous solution when it serves as the anode of a voltaic cell.

Verified step by step guidance

1. Identify the role of the hydrogen electrode in the voltaic cell. Since it is serving as the anode, oxidation occurs at this electrode.
2. Write the initial state of hydrogen in acidic solution. In acidic solutions, hydrogen is typically present as $H^+$ ions.
3. Determine the oxidation half-reaction. During oxidation at the anode, hydrogen gas ($H_2$) is oxidized to hydrogen ions ($H^+$).
4. Balance the hydrogen atoms in the half-reaction. Since each hydrogen molecule consists of two hydrogen atoms, the reaction will involve two $H^+$ ions for each $H_2$ molecule.
5. Balance the charge by adding electrons. Two electrons are needed on the product side to balance the charges, as each $H^+$ ion carries a charge of +1.

Key Concepts

Half-Reaction

A half-reaction represents either the oxidation or reduction process occurring in an electrochemical cell. In the context of a voltaic cell, the anode undergoes oxidation, where electrons are released. Understanding half-reactions is crucial for balancing redox reactions and determining the flow of electrons in electrochemical systems.

Voltaic Cell

A voltaic cell, also known as a galvanic cell, is an electrochemical cell that converts chemical energy into electrical energy through spontaneous redox reactions. It consists of two electrodes (anode and cathode) immersed in electrolyte solutions. The anode is where oxidation occurs, while reduction takes place at the cathode, generating a flow of electrons that can be harnessed for electrical power.

Acidic Aqueous Solution

An acidic aqueous solution contains a higher concentration of hydrogen ions (H+) than hydroxide ions (OH-), typically with a pH less than 7. In the context of the hydrogen electrode, the presence of H+ ions facilitates the reduction of protons to hydrogen gas at the cathode or the oxidation of hydrogen gas to protons at the anode. This environment is essential for understanding the reactions that occur at the hydrogen electrode in electrochemical cells.