Pure water is actually a mixture of water molecules, hydronium ions, and hydroxide ions:
A. How does the concentration of hydroxide ions compare to the concentration of hydronium ions in pure water?Explain
B. How does the concentration of ions compare to the concentration of molecules in pure water?

A. They are equal.

B. The ratio of ions to molecules is 1 to 2.78× 10⁸.

Explanation:

A. Concentration of ions

In pure water, [H₃O⁺] = [OH⁻] = 1.00 × 10⁻⁷ mol·L⁻¹.

The concentration of hydroxide ions equals that of hydronium ions.  

B. Ratio of ions to molecules

Assume you have 1 L of pure water.

You have 1.00× 10⁻⁷ mol·L⁻¹ [H₃O⁺] and 1.00× 10⁻⁷ mol·L⁻¹ [OH⁻], so you have 2,00 mol·L⁻¹ of ions.

The ratio of concentrations is  

yes it is balanced