Calculate The Ph of A 0.05 M Solution of Naoh

Sodium hydroxide (NaOH) is a strong base that completely dissociates in water. This calculator determines the pH of a 0.05 molar (M) solution of NaOH using the standard pH calculation method for strong bases.

Introduction

The pH of a solution is a measure of its acidity or alkalinity. For strong bases like NaOH, the pH can be calculated directly from the concentration of the hydroxide ions (OH⁻).

When NaOH dissolves in water, it dissociates completely into sodium ions (Na⁺) and hydroxide ions (OH⁻). The concentration of hydroxide ions is equal to the concentration of the NaOH solution.

pH Calculation Formula

The pH of a strong base solution is calculated using the following formula:

pH = 14 + log[OH⁻]

Where:

pH - the measure of acidity or alkalinity
[OH⁻] - the concentration of hydroxide ions in moles per liter (M)

For a 0.05 M solution of NaOH:

pH = 14 + log(0.05)

pH = 14 + (-1.3010) = 12.6990

Worked Example

Let's calculate the pH of a 0.05 M NaOH solution step by step:

Identify the concentration of hydroxide ions: [OH⁻] = 0.05 M
Take the logarithm (base 10) of the hydroxide ion concentration: log(0.05) = -1.3010
Add 14 to the logarithm result: 14 + (-1.3010) = 12.6990
Round to two decimal places: pH ≈ 12.70

The pH of a 0.05 M NaOH solution is approximately 12.70, indicating a strongly alkaline solution.

Interpreting Results

A pH of 12.70 means the solution is:

Highly alkaline (basic)
Strongly corrosive to metals and skin
Not neutral (pH 7)
Less acidic than a pH 1 solution

Safety Note: NaOH solutions are caustic and can cause severe burns. Always handle with proper protective equipment.

FAQ

Why does NaOH have a pH of 12.70 at 0.05 M?: Because it's a strong base that completely dissociates in water, creating equal concentrations of Na⁺ and OH⁻ ions. The pH is calculated directly from the hydroxide ion concentration.
What happens if the NaOH concentration changes?: The pH will change proportionally. Higher concentrations result in higher pH values (more alkaline), while lower concentrations result in lower pH values.
Is this formula accurate for all strong bases?: Yes, this formula applies to any strong base that completely dissociates in water, including KOH and LiOH.
What if the solution is diluted?: Dilution decreases the concentration of hydroxide ions, lowering the pH. You would need to recalculate using the new concentration.
Can I use this for weak bases?: No, this formula only applies to strong bases. Weak bases require a different calculation method that accounts for their partial dissociation.