Question

Ions, when an ionic compound is dissolved in water, can best be described as:

• A. hydrated molecules only
• B. both dehydrated ions and molecules
• C. hydrated ions only
• D. neither hydrated ions nor hydrated molecules
• E. none of these

Answer 1

The correct option is C hydrated ions only

Ionic compounds dissolve in water because the water molecules hydrate the ions. To dissolve an ionic compound, the water molecules must be able to stabilize the ions that result from breaking the ionic bond. They do this by hydrating the ions.

Water is a polar molecule. It has a permanent dipole. The $O$ atom has a partial negative charge. The $H$ atoms have a partial positive charge. When an ionic substance is placed in water, the water molecules attract the positive and negative ions from the crystal. The positive ions have several water molecules around them, all with their $O$ atoms close to the positive ion. The negative ions have several water molecules around them, all with their $H$ atoms close to the negative ion.

The "shell" of water molecules reduces the attraction between the ions. The ions are hydrated.

Hence, option C is correct.