When a 0.25 m solution of sucrose (C12H22O11) in water is tested for conductivity, the bulb will not light up. This is because sucrose is a non-electrolyte.
To explain further, substances can be classified as electrolytes or non-electrolytes based on their ability to conduct electricity when dissolved in water. Electrolytes are substances that dissociate into ions in solution, which can carry an electric current. Common electrolytes include salts, acids, and some bases.
On the other hand, sucrose does not dissociate into ions when it dissolves in water. Instead, it remains as whole molecules. Since there are no charged particles (ions) in the solution, there is no electric current to pass through, and thus the bulb will not light up. Therefore, it is inaccurate to describe sucrose as an electrolyte; it is indeed a non-electrolyte.