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Chemistry · Grades 10–12

pOH at 25 °C

The sum pH + pOH is approximately 14 for the stated dilute aqueous model at 25 °C; it changes with temperature.

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Rule and assumptions

The sum pH + pOH is approximately 14 for the stated dilute aqueous model at 25 °C; it changes with temperature.

pOH ≈ 14 − pH at 25 °C

Worked examples

At 25 °C, use the dilute model pH + pOH = 14. A solution has pH 6.6. Find pOH. Round to 3 decimal places if needed.

pOH ≈ 14 − pH at 25 °C 14 − 6.6 = 7.4

7.4

At 25 °C, use the dilute model pH + pOH = 14. A solution has pH 3. Find pOH. Round to 3 decimal places if needed.

pOH ≈ 14 − pH at 25 °C 14 − 3 = 11

11

Try two questions

  1. At 25 °C, use the dilute model pH + pOH = 14. A solution has pH 7.7. Find pOH. Round to 3 decimal places if needed.

  2. At 25 °C, use the dilute model pH + pOH = 14. A solution has pH 1.9. Find pOH. Round to 3 decimal places if needed.

Answers and reasoning

Answers and marking notes
  1. 6.3

    pOH ≈ 14 − pH at 25 °C 14 − 7.7 = 6.3

  2. 12.1

    pOH ≈ 14 − pH at 25 °C 14 − 1.9 = 12.1

Further reading and review references

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Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.