Science, Tech, Math › Science Acids and Bases - Calculating pH of a Strong Base Worked Chemistry Problems Share Flipboard Email Print A rainbow wand shows a gradual change of pH. If you were to separate out all the different pH levels, this is what you would see. Don Bayley, Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Todd Helmenstine Todd Helmenstine is a science writer and illustrator who has taught physics and math at the college level. He holds bachelor's degrees in both physics and mathematics. our editorial process Todd Helmenstine Updated May 07, 2019 KOH is an example of a strong base, which means it dissociates into its ions in aqueous solution. Although the pH of KOH or potassium hydroxide is extremely high (usually ranging from 10 to 13 in typical solutions), the exact value depends on the concentration of this strong base in water. So, it's important to know how to perform the pH calculation. Strong Base pH Question What is the pH of a 0.05 M solution of Potassium Hydroxide? Solution Potassium Hydroxide or KOH, is a strong base and will dissociate completely in water to K+ and OH-. For every mole of KOH, there will be 1 mole of OH-, so the concentration of OH- will be the same as the concentration of KOH. Therefore, [OH-] = 0.05 M. Since the concentration of OH- is known, the pOH value is more useful. pOH is calculated by the formula pOH = - log [OH-] Enter the concentration found before pOH = - log (0.05)pOH = -(-1.3)pOH = 1.3 The value for pH is needed and the relationship between pH and pOH is given by pH + pOH = 14 pH = 14 - pOHpH = 14 - 1.3pH = 12.7 Answer The pH of a 0.05 M solution of Potassium Hydroxide is 12.7.