Chemistry · Grades 10–12
pH from a supplied concentration
Use the dilute idealized aqueous model; concentrations approximate activities.
Rule and assumptions
Use the dilute idealized aqueous model; concentrations approximate activities.
pH ≈ −log₁₀([H₃O⁺]/(1 mol/L))
Worked examples
In the dilute school model, [H₃O⁺] = 9 × 10^−5 mol/L. Calculate pH. Round to 3 decimal places if needed.
pH ≈ −log₁₀([H₃O⁺]/(1 mol/L)) 5 − log₁₀(9) = 4.046
4.046
In the dilute school model, [H₃O⁺] = 4 × 10^−5 mol/L. Calculate pH. Round to 3 decimal places if needed.
pH ≈ −log₁₀([H₃O⁺]/(1 mol/L)) 5 − log₁₀(4) = 4.398
4.398
Try two questions
In the dilute school model, [H₃O⁺] = 7 × 10^−4 mol/L. Calculate pH. Round to 3 decimal places if needed.
In the dilute school model, [H₃O⁺] = 1 × 10^−4 mol/L. Calculate pH. Round to 3 decimal places if needed.
Answers and reasoning
Answers and marking notes
- 3.155
pH ≈ −log₁₀([H₃O⁺]/(1 mol/L)) 4 − log₁₀(7) = 3.155
- 4
pH ≈ −log₁₀([H₃O⁺]/(1 mol/L)) 4 − log₁₀(1) = 4
Further reading and review references
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Learning preview · independent educational and translation review required. Suggested grades are not official curriculum alignment.