Question

Molten NaCl conduct electricity due to the presence of:
A, Free molecules
B. Free ions
C. Free electrons
D. Free atoms

Answer 1

Hint: Conductivity of metals or ionic compounds depend upon the presence of free electrons or free ions. The conductivity of the ionic compound depends upon the ionization of that compound in an aqueous solution.

Complete step by step solution:
Conductivity is the ability to conduct electricity which depends upon the presence of free electrons as well as free ions. So, to conduct electricity charged particles are required. The presence of electrons or free ions causes conductivity.
Free molecules do not conduct electricity because they are not charged.
In an ionic compound, such as solid sodium chloride the free electrons are not present. Electrons are bound in bonds by strong electrostatic forces. So, sodium chloride does not conduct electricity in a solid-state. In a molten state, sodium chloride dissociates into a sodium ion and chloride ion and these ions conduct electricity.
The metal conducts electricity in solid due to the presence of electrons for example, copper metal.
Free atoms do not conduct electricity because they are not charged.
So, the reason for the conductivity of sodium chloride in the molten state is the presence of free ions.

Therefore, option (B) free ions, is correct.

Note: The conductivity of metal is due to the free electrons which present in both the solid and molten state whereas the conductivity of the ionic compound is due to ions that are present in the solid-state but becomes free only in the molten state. As the number of free electrons increases the conductivity of metal increases. Conductivity also depends upon the size of the ions. The small ions become more hydrated in an aqueous solution, so the conductivity decreases on decreasing the size of the ion.