Question

a salt bridge containing potassium nitrate connects an anode and cathode in a voltaic cell. which answer correctly describes the movement of no₃⁻ ions? the no₃⁻ ions move across the voltmeter to neutralize the electrons. the no₃⁻ ions flow into the cathode compartment to neutralize the excess charge. the no₃⁻ ions flow into the anode compartment to neutralize the excess charge. the no₃⁻ ions do not move. they provide a pathway for electrons to travel through the salt bridge.

Explanation:

In a voltaic cell, at the anode, oxidation occurs (electrons are released, leaving a positive charge in the anode compartment). At the cathode, reduction occurs (electrons are consumed, leaving a negative charge in the cathode compartment). The salt bridge's ions move to neutralize excess charge. \( \text{NO}_3^- \) is an anion (negative charge). Anions move towards the anode (where there is excess positive charge) to neutralize it. Let's analyze each option:

• Option 1: Ions don't move through the voltmeter (electrons move through the external circuit, ions through the salt bridge). Eliminate.
• Option 2: \( \text{NO}_3^- \) (anion) should move to anode, not cathode. Eliminate.
• Option 3: Anode has excess positive charge (from oxidation, electrons leave, so more positive ions). \( \text{NO}_3^- \) (negative) moves to anode to neutralize. Correct.
• Option 4: Ions do move in the salt bridge, and electrons don't travel through the salt bridge (they go through the external wire). Eliminate.

Answer:

The \( \text{NO}_3^- \) ions flow into the anode compartment to neutralize the excess charge.