pH/pOH Calculations

Front

What is pH?

Back

pH is a measure of the hydrogen ion concentration in a solution, defined as pH = -log[H₃O⁺]. It indicates how acidic or basic a solution is.

Front

What is pOH?

Back

pOH is a measure of the hydroxide ion concentration in a solution, defined as pOH = -log[OH⁻]. It indicates how basic a solution is.

Front

What is the relationship between pH and pOH?

Back

pH + pOH = 14 at 25°C. This relationship shows that as the acidity of a solution increases (lower pH), the basicity decreases (higher pOH), and vice versa.

Front

How do you calculate pH from [H₃O⁺]?

Back

To calculate pH from the hydronium ion concentration, use the formula: pH = -log[H₃O⁺]. For example, if [H₃O⁺] = 1 x 10⁻³ M, then pH = 3.

Front

How do you calculate pOH from [OH⁻]?

Back

To calculate pOH from the hydroxide ion concentration, use the formula: pOH = -log[OH⁻]. For example, if [OH⁻] = 2.7 x 10⁻⁴ M, then pOH = 3.57.

Front

What is the pH of a neutral solution at 25°C?

Back

The pH of a neutral solution at 25°C is 7, indicating equal concentrations of H₃O⁺ and OH⁻.

Front

What does a pH less than 7 indicate?

Back

A pH less than 7 indicates an acidic solution, meaning there is a higher concentration of H₃O⁺ ions compared to OH⁻ ions.

Front

What does a pH greater than 7 indicate?

Back

A pH greater than 7 indicates a basic (alkaline) solution, meaning there is a higher concentration of OH⁻ ions compared to H₃O⁺ ions.

Front

If [H₃O⁺] = 1.0 x 10⁻⁴ M, what is the pH?

Back

pH = -log(1.0 x 10⁻⁴) = 4.

Front

If [OH⁻] = 1.0 x 10⁻⁵ M, what is the pOH?

Back

pOH = -log(1.0 x 10⁻⁵) = 5.