Chemistry

Chemistry

Problem

At 37 °C, the ion-product constant of water is approximately 2.5×10−142.5\times10^{-14}. If a solution at this temperature has pOH = 3.60, what is its pH? a) 10.4010.40 b) 13.6013.60 c) 10.0010.00 d) 9.809.80
Intuitive explanation

The key is recognizing that Kw=[H+][OH−]K_w = [H^+][OH^-] still holds at any temperature, even though its value changes from the familiar 10−1410^{-14} at 25 °C. Once you find [OH−][OH^-] from the given pOH, you can calculate [H+][H^+] using the new KwK_w, then convert to pH—the relationship between pH and pOH shifts when temperature changes.

Intuitive explanation

The key is recognizing that Kw=[H+][OH−]K_w = [H^+][OH^-] still holds at any temperature, even though its value changes from the familiar 10−1410^{-14} at 25 °C. Once you find [OH−][OH^-] from the given pOH, you can calculate [H+][H^+] using the new KwK_w, then convert to pH—the relationship between pH and pOH shifts when temperature changes.

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