A student observes that solid substance “X” does not conduct electricity but conducts when melted, while substance “Y” does not conduct electricity in any state. What is the most appropriate classification of “X” and “Y”?
Correct answer: B. X is an ionic crystal; Y is a molecular crystal
- A. X is a molecular crystal, Y is an ionic crystal
- B. X is an ionic crystal; Y is a molecular crystal
- C. Both X and Y are ionic crystals
- D. Both X and Y are molecular crystals
Explanation
An ionic crystal does not conduct as a solid because its ions are fixed, but conducts when molten as the ions become free to move, so X is ionic. A molecular crystal has no ions or free electrons in any state, so Y is molecular. Option a reverses the two.
This question appeared on the UHS MDCAT 2026 paper, which you can sit online with every answer explained.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
About Ionic and Molecular Crystals
Ionic crystals contain oppositely charged ions held by electrostatic forces, whereas molecular crystals contain discrete molecules joined by weaker intermolecular forces. Their structures explain differences in melting point, hardness, volatility, solubility and electrical conductivity, especially between solid and molten states.
Practise Solids
361 free Solids MCQs from Chemistry, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Chemistry questions like this
Chemistry is on 14 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.