Q19.
What type of chemical bond is present in a solid compound that does not conduct electricity in the solid state but conducts electricity when dissolved in water?
Answer
An ionic bond. That pair of observations is the standard fingerprint of an ionic compound.
- No conduction as a solid — the ions are there, but they are clamped in fixed positions in the crystal lattice by strong electrostatic forces, so no charge can move.
- Conduction in water — water pulls the lattice apart and sets the ions free. Once mobile, the cations drift towards the negative electrode and the anions towards the positive one, and that drift is the current.
Sodium chloride and copper sulfate both behave exactly like this, as Activity 9.4 shows.
Why it happens: the two clues must be read together. Conduction in solution alone would not settle it — you would still have to rule out a covalent compound like sugar, which dissolves but does not conduct. It is the combination — ions present but immobile in the solid, mobile once dissolved — that points uniquely to ionic bonding.
Check it yourself: such compounds also melt at high temperatures, because pulling apart a lattice of oppositely charged ions takes a lot of energy. Common salt melts at about 800 °C; camphor, a covalent solid, melts below 180 °C.