From past weeks · Chemistry
Dilute a strong acid ten times. What is the new pH?
Predict
A strong acid has a pH of 1.0. You dilute it by a factor of 10 with water. What is the new pH?
Test it
Add water and watch the pH, the hydrogen ion concentration and the ions in one small sample.
Why
Answer: 2
A strong acid is fully ionised, so at pH 1.0 the hydrogen ion concentration is 0.1 mol/L. Ten times the volume makes it 0.01 mol/L.
pH = −log₁₀[H⁺], a logarithmic scale: a tenfold drop in [H⁺] raises the pH by just 1, from 1.0 to 2.0. It is still an acid.
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