Calculate The Ph of 0.075 M Koh

Potassium hydroxide (KOH) is a strong base that completely dissociates in water. This calculator determines the pH of a 0.075 molar (M) KOH solution using the standard pH calculation method for strong bases.

Introduction

The pH scale measures how acidic or basic a solution is. For strong bases like KOH, we can calculate the pH directly from the concentration using the formula:

pH = 14 + log₁₀([OH^-])

Since KOH is a strong base, it completely dissociates in water, so the concentration of hydroxide ions ([OH^-]) equals the concentration of KOH.

pH Calculation Formula

The pH of a strong base solution can be calculated using the following steps:

Determine the concentration of hydroxide ions ([OH^-]) which equals the concentration of KOH.
Calculate the negative logarithm (base 10) of the hydroxide ion concentration.
Add 14 to this value to get the pH.

pH = 14 + log₁₀([KOH])

For a 0.075 M KOH solution:

pH = 14 + log₁₀(0.075) ≈ 12.12

Worked Example

Let's calculate the pH of a 0.075 M KOH solution step by step:

Given: [KOH] = 0.075 M
Since KOH is a strong base, [OH^-] = [KOH] = 0.075 M
Calculate log₁₀(0.075) ≈ -1.1239
pH = 14 + (-1.1239) ≈ 12.8761
Rounded to two decimal places: pH ≈ 12.88

This confirms our calculator's result of approximately 12.88 for 0.075 M KOH.

Interpreting Results

A pH of 12.88 indicates a strongly basic solution. This is typical for concentrated KOH solutions. The hydroxide ion concentration is 0.075 M, meaning there are 0.075 moles of OH^- per liter of solution.

This level of basicity is strong enough to:

Neutralize most acids completely
Dissolve many metals
Provide strong alkaline conditions for chemical reactions

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

FAQ

What is the pH of 0.075 M KOH?: The pH of 0.075 M KOH is approximately 12.88.
Why is the pH of KOH calculated differently than weak bases?: KOH is a strong base that completely dissociates in water, so we can directly use its concentration to calculate pH without considering equilibrium.
How does temperature affect the pH of KOH solutions?: The pH calculation assumes standard temperature conditions (25°C). At different temperatures, the pH may change slightly due to temperature effects on dissociation.
Can I use this calculator for other strong bases?: Yes, this method applies to any strong base solution where the concentration is known.
What is the pH range for strong bases?: Strong bases typically have pH values between 12 and 14, with higher concentrations resulting in higher pH values.