It is common to add Epson salts to bath water when one has been over exercising and has sore muscles. What is the primary intermolecular force that exists between magnesium sulfate, the primary in Epson salts, and the water in the bathtub?

• A. dipole-dipole forces
• B. ion-dipole forces
• C. London forces
• D. Hydrogen bonding

Answer: (B)

Verified step by step guidance

1. Identify the chemical nature of magnesium sulfate (MgSO₄). It is an ionic compound composed of magnesium ions (Mg²⁺) and sulfate ions (SO₄²⁻).
2. Recognize that water (H₂O) is a polar molecule with a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom.
3. Understand that when an ionic compound like magnesium sulfate dissolves in water, the ions interact with the polar water molecules.
4. Determine the type of intermolecular force: Ion-dipole forces occur between the charged ions of the solute (Mg²⁺ and SO₄²⁻) and the dipole of the solvent (water molecules).
5. Conclude that the primary intermolecular force between magnesium sulfate and water is ion-dipole forces, as the ions are attracted to the opposite partial charges on the water molecules.