How to Calculate the pH of a Potassium Hydroxide Solution

What are the steps to calculate the pH of a potassium hydroxide solution?

How do we determine the moles of potassium hydroxide in the solution and what is the equation to find the pH?

Steps to Calculate the pH of a Potassium Hydroxide Solution

To calculate the pH of a potassium hydroxide solution, we first need to find the moles of potassium hydroxide (KOH) in the solution and the volume of the solution. The pH can then be determined using the formula involving hydroxide ions (OH-).

When given the mass of KOH and the volume of the solution, we can calculate the moles of KOH using the formula: moles = mass / molar mass. For KOH, the molar mass is 56.11 g/mol.

Given: mass of KOH = 805 mg = 0.805 g, volume of solution = 130 mL = 0.13 L

The moles of KOH = 0.805 g / 56.11 g/mol = 0.01436 mol. Since KOH is a strong base, it completely dissociates in water to form one mole of hydroxide ions for every mole of KOH.

The concentration of OH- ions = moles of KOH / volume of solution = 0.01436 mol / 0.13 L = 0.1103 M.

The pH of a basic solution can be calculated using the equation: pH = 14 - pOH. First, find pOH using the formula: pOH = -log10[OH-]. Plugging in the values, pOH = -log10(0.1103) = 0.9581. Finally, calculate the pH: pH = 14 - 0.9581 = 13.0419.

Rounded to 3 significant decimal places, the pH of the potassium hydroxide solution is 13.042.