Question 1
Multiple choiceMedium1 markAn ionic solid is made from X²⁺ and Y⁻ ions in a three-dimensional lattice. Which description gives both its empirical formula and its electrical conductivity in the solid and molten states?
Show answer and explanation
Answer: C. One X²⁺ requires two Y⁻ ions to give an electrically neutral formula, XY₂. In the solid lattice, ions are fixed in position and cannot carry charge through the solid. When molten, the ions are mobile and conduct electricity.
A: assumes a 1:1 ion ratio, so the formula does not balance charge.
B: reverses the conductivity behaviour: ions are fixed in the solid but mobile when molten.
D: assumes ions cannot conduct even when molten, overlooking their mobility.
Remember: ionic compounds conduct when their ions are mobile.