Final answer:
An aqueous KCl solution conducts electricity due to the presence and mobility of K+ and Cl- ions, making it an electrolyte. Sucrose solutions do not conduct electricity because they contain no ions, classifying sucrose as a nonelectrolyte. Ion mobility is key for a solution's conductivity.
Step-by-step explanation:
An aqueous solution of KCl conducts electricity because potassium chloride is an electrolyte. When KCl dissolves in water, it dissociates into potassium (K+) and chloride (Cl-) ions. These ions are free to move in the solution, allowing electric current to pass through. The presence of mobile charged particles is essential for electrical conductivity. On the other hand, a solution of sucrose does not conduct electricity because sucrose is a nonelectrolyte. It dissolves in water as molecules, not ions. Since there are no charged particles to carry the current, sucrose solutions do not allow electricity to flow.
Understanding Electrolytes and Conductivity
The conductivity of an electrolyte solution is directly related to the presence and mobility of ions in the solution. When an electrolyte such as KCl is dissolved, it contributes to the current because each type of ion (K+ and Cl-) makes an independent contribution. Conversely, nonelectrolytes like sucrose do not produce ions when dissolved and therefore do not contribute to electrical conductivity. The beaker experiments demonstrate that ion mobility is crucial for conducting electric currents in solutions.