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Calculate The Ph of 0.1 M Koh

Reviewed by Calculator Editorial Team

Potassium hydroxide (KOH) is a strong base that completely dissociates in water to produce hydroxide ions (OH⁻). This calculator helps you determine the pH of a 0.1 molar (M) KOH solution using the standard pH calculation method for strong bases.

How to Calculate the pH of 0.1 M KOH

To calculate the pH of a 0.1 M KOH solution, follow these steps:

  1. Determine the molarity of the KOH solution (0.1 M in this case).
  2. Recognize that KOH is a strong base that completely dissociates in water.
  3. Calculate the concentration of hydroxide ions ([OH⁻]) using the molarity.
  4. Use the relationship between [OH⁻] and pOH to find pOH.
  5. Convert pOH to pH using the relationship pH + pOH = 14.

Note: This method is valid for strong bases like KOH where the assumption of complete dissociation holds true.

The pH Calculation Formula

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

1. [OH⁻] = Molarity of KOH (M)

2. pOH = -log[OH⁻]

3. pH = 14 - pOH

For a 0.1 M KOH solution:

[OH⁻] = 0.1 M

pOH = -log(0.1) = 1

pH = 14 - 1 = 13

Worked Example

Let's calculate the pH of a 0.1 M KOH solution step by step:

  1. Given: Molarity of KOH = 0.1 M
  2. Since KOH is a strong base, [OH⁻] = 0.1 M
  3. Calculate pOH: pOH = -log(0.1) = 1
  4. Calculate pH: pH = 14 - pOH = 14 - 1 = 13

The pH of a 0.1 M KOH solution is 13.

Interpreting the Result

A pH of 13 indicates that the solution is strongly alkaline. This is expected for a strong base like KOH, which completely dissociates in water to produce hydroxide ions. The high pH value reflects the high concentration of OH⁻ ions in the solution.

In practical terms, this solution would feel slippery to the touch and would turn red litmus paper blue. It would also react strongly with acids to form water and a salt.

Frequently Asked Questions

Why is the pH of 0.1 M KOH 13?
The pH is 13 because the hydroxide ion concentration ([OH⁻]) is 0.1 M, and pH = 14 - pOH. For a strong base like KOH, the molarity equals the [OH⁻] concentration.
Can this method be used for weak bases?
No, this method is specifically for strong bases that completely dissociate in water. Weak bases require a different approach using equilibrium constants.
What happens if the KOH concentration changes?
The pH will change proportionally. For example, a 0.01 M KOH solution would have a pH of 12, and a 1 M KOH solution would have a pH of 14.