pOH Calculator

What is pOH?

pOH is a scale that measures how basic (or alkaline) a water-based solution is. It focuses on the concentration of hydroxide ions (OH⁻). The more OH⁻ ions present, the more basic the solution, and the lower its pOH value.

Think of pOH as the "opposite" of pH. While pH tells us about acidity (hydrogen ions), pOH tells us about basicity (hydroxide ions). They are directly linked: pH + pOH = 14 at 25°C. This means if you know one, you can easily find the other!

The pOH Scale Explained

The pOH scale, like the pH scale, typically ranges from 0 to 14. Here's how to interpret it:

• pOH less than 7: The solution is basic (alkaline). The lower the pOH, the stronger the base. (e.g., drain cleaner, bleach)
• pOH equal to 7: The solution is neutral. Pure water at room temperature has a pOH of 7 (and a pH of 7).
• pOH greater than 7: The solution is acidic. The higher the pOH, the stronger the acid (because it means very few OH⁻ ions).
• Each unit change on the pOH scale represents a tenfold change in the concentration of hydroxide ions. For example, a solution with a pOH of 3 has ten times more OH⁻ than a solution with a pOH of 4.

Why are pOH and Basicity Important?

Understanding pOH and basicity is crucial in many different fields:

• Cleaning Products: Many household cleaners (like bleach, ammonia, oven cleaner) are basic. Their effectiveness often depends on their high pOH.
• Water Treatment: Controlling the pH (and thus pOH) of drinking water and wastewater is essential for safety, preventing corrosion, and effective purification.
• Agriculture: Soil pH (and pOH) affects how well plants can absorb nutrients. Farmers often adjust soil pH to optimize crop growth.
• Industrial Processes: Many chemical reactions in manufacturing require specific basic conditions to proceed correctly, which means controlling the pOH.
• Biology & Medicine: Our bodies maintain a very precise pH balance in blood and other fluids. While pH is usually discussed, pOH is equally important for understanding this delicate balance, especially in relation to metabolic processes.

Common Solutions and Their pOH Values

Here are some everyday examples to help you understand the pOH scale:

• Drain Cleaner: pOH ~0-1 (Very strong base)
• Bleach: pOH ~1-2 (Strong base)
• Ammonia (Household): pOH ~2-3 (Base)
• Baking Soda Solution: pOH ~5 (Mild base)
• Pure Water: pOH 7.0 (Neutral)
• Human Blood: pOH ~6.6 (Slightly acidic from pOH perspective, slightly basic from pH perspective)
• Lemon Juice: pOH ~12 (Acidic)
• Battery Acid: pOH ~13-14 (Very strong acid)