Assertion (A): Copper sulfate conducts electricity in the molten state but not in the solid state. Reason (R): Copper and sulfate ions are fixed in the lattice in molten state, while in solid state they can move freely.
Explanation
Assertion (A) is true because ionic compounds like copper sulfate do not conduct electricity in the solid state as their ions are held in fixed positions by strong forces, but they conduct electricity in the molten state where ions are free to move. Reason (R) is false because it reverses the facts: ions are fixed in the lattice in the solid state, not the molten state, and they can move freely in the molten state, not the solid state.
Solution Steps
Step 1: Evaluate Assertion (A). The context states that ionic compounds do not conduct electricity in the solid state because their ions are held in fixed positions, but they conduct when melted. Thus, A is true.
Step 2: Evaluate Reason (R). The context states ions are fixed in the solid state and must be free to move to conduct electricity (which occurs in molten or dissolved states). R reverses this by claiming ions are fixed in the molten state and move freely in the solid state. Thus, R is false.
Step 3: Match with the given options. Since A is true and R is false, option (iii) is the correct choice.