Which of the following substances would be a poor conductor of electricity?

• A. KNO_3 dissolved in water
• B. NaCl dissolved in water
• C. HCl dissolved in water
• D. C_6H_{12}O_6 (glucose) dissolved in water

Answer: (D)

Verified step by step guidance

1. Understand that electrical conductivity in aqueous solutions depends on the presence of ions that can move freely and carry charge.
2. Recognize that substances like KNO_3, NaCl, and HCl are electrolytes because they dissociate into ions (K^+, NO_3^-, Na^+, Cl^-, H^+, and Cl^-) when dissolved in water, allowing the solution to conduct electricity well.
3. Identify that C_6H_{12}O_6 (glucose) is a molecular compound that dissolves in water but does not dissociate into ions; it remains as neutral molecules in solution.
4. Conclude that since glucose does not produce ions in solution, it cannot conduct electricity effectively, making it a poor conductor compared to the ionic compounds listed.
5. Therefore, the key to determining conductivity is whether the substance dissociates into ions in water; ionic compounds and strong acids do, while molecular compounds like glucose do not.