pH scale explorer

The pH scale compresses a huge range of acidities into numbers from 0 to 14. In this simulation you test everyday liquids with a virtual probe, adjust concentrations, and dilute solutions to see the logarithmic scale in action. Learning goals: relate pH values to hydronium ion concentration; explain why each pH unit is a tenfold change; predict how dilution shifts the pH of an acidic or basic solution.

pH: 7

pH 7.0 — Neutral

[H⁺] = 1.0e-7 M · [OH⁻] = 1.0e-7 M

Each pH unit is a 10× change in [H⁺]. pH 3 is ten times more acidic than pH 4.

Controls

Solution selection: Picks a household or lab solution to place under the pH probe.
Concentration slider: Sets the starting molarity of the chosen acid or base.
Dilute: Adds pure water, lowering the concentration and shifting pH toward 7.
Show [H3O+]: Displays the hydronium ion concentration alongside the pH value.

The chemistry

\text{pH} = -\log_{10}[\text{H}_3\text{O}^+]

Definition of pH

[\text{H}_3\text{O}^+] = 10^{-\text{pH}}

Hydronium concentration from pH

K_w = [\text{H}_3\text{O}^+][\text{OH}^-] = 1.0 \times 10^{-14}

Water autoionization at 25°C

Assumptions

Only strong acids and bases are modeled, so they dissociate completely.
Temperature is 25°C and concentration approximates activity.
The pH meter responds instantly and ideally.

Guided activity

Select lemon juice and note its pH, then dilute it and watch the pH rise.
Compare the pH of vinegar and baking soda solution and explain the difference.
Find which household solution in the simulation is closest to neutral.
Dilute a strong acid tenfold and verify the pH rises by about 1 unit.

Challenge questions

Arrange five solutions from most acidic to most basic without looking at the pH numbers first.
Predict the pH after diluting a pH 2 solution tenfold, then test it.
Explain why diluting an acid raises its pH but never makes it basic.