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Chemistry & Materials Science

pOH Calculator

Calculate the pOH, pH, and hydrogen ion concentration from the given hydroxide ion concentration [OH-] for a complete solution profile.

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Convert hydroxide ion concentration [OH−][OH^-] into pOH. Understanding pOH is essential for determining the alkalinity and basicity of solutions, and this calculator instantly cross-computes the corresponding pH and [H+][H^+] values.

The pOH Scale

Just as pH measures the concentration of protons, pOH measures the concentration of hydroxide ions. In any aqueous solution at standard temperature (25∘C25^\circ\text{C}), the sum of pH and pOH is always exactly 14.

pOH=−log⁡10[OH−]\begin{aligned} \text{pOH} = -\log_{10}[OH^-] \end{aligned}

Where:
[OH−][OH^-]=
Hydroxide Ion Concentration (mol/L)

Applications in Basicity

While pH is universally recognized, pOH is specifically useful when working directly with strong bases like Sodium Hydroxide (NaOH) or Potassium Hydroxide (KOH), where the [OH−][OH^-] concentration is known from the start.

Frequently Asked Questions

At standard temperature (25∘C25^\circ\text{C}), the relationship is strictly defined by the autoionization of water: pH+pOH=14\text{pH} + \text{pOH} = 14.

A high pOH (e.g., 12) means there is very little hydroxide in the solution, which corresponds to a low pH (e.g., 2). Therefore, a high pOH indicates a highly acidic solution.

You can reverse the logarithmic function by taking the antilog: [OH−]=10−pOH[OH^-] = 10^{-\text{pOH}}.

While pH is the standard metric displayed on meters and regulatory documents, pOH is frequently used internally by chemists when formulating strong alkaline cleaning agents, bleaches, and titrants.

Yes. The constant KwK_w changes with temperature. At higher temperatures, water autoionizes more, so neutral water will have a pOH (and pH) slightly lower than 7.

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