At 25°C, what is the relationship between pH and pOH?

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Multiple Choice

At 25°C, what is the relationship between pH and pOH?

Explanation:
At 25°C, pH and pOH are linked by their sum being 14. This comes from the autoionization of water: Kw = [H+][OH−] = 1.0×10−14 at this temperature. Since pH = −log[H+] and pOH = −log[OH−], adding them gives pH + pOH = −log([H+][OH−]) = −log(Kw) = 14. So the relationship is pH plus pOH equals 14. This holds specifically at 25°C; if the temperature changes, Kw changes and the sum is no longer exactly 14. For neutral water, pH and pOH are both 7, which also fits this rule. Other formulations don’t work because they imply different mathematical relations that don’t reflect how pH and pOH are defined from Kw and the logarithm properties.

At 25°C, pH and pOH are linked by their sum being 14. This comes from the autoionization of water: Kw = [H+][OH−] = 1.0×10−14 at this temperature. Since pH = −log[H+] and pOH = −log[OH−], adding them gives pH + pOH = −log([H+][OH−]) = −log(Kw) = 14. So the relationship is pH plus pOH equals 14.

This holds specifically at 25°C; if the temperature changes, Kw changes and the sum is no longer exactly 14. For neutral water, pH and pOH are both 7, which also fits this rule.

Other formulations don’t work because they imply different mathematical relations that don’t reflect how pH and pOH are defined from Kw and the logarithm properties.

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