pH & Titration
pH & Titration is a free interactive simulation from StudyFi Lab. It runs right in your browser, with no sign-up and nothing to install.
Drip acid or base and watch the pH and the titration curve
Experiments
Free mixing
The beaker holds 50 mL of water with universal indicator. pH = −log[H⁺]: every drop of acid adds H⁺ ions, every drop of NaOH adds OH⁻ ions, which combine with H⁺ to form water. The scale is logarithmic, so ten times more H⁺ moves the pH by only 1. In water [H⁺]·[OH⁻] = 10⁻¹⁴.
Try this: Add one small drop of HCl, then try to get back to exactly pH 7 with drops of NaOH. Why is it so hard?
Challenge: hit the pH
The beaker holds 50 mL of dilute acetic acid (pH about 3.2). Use drops of NaOH and acid to reach the target pH within ± 0.2. Acetic acid and acetate form a buffer, so around pH 4–6 the pH moves slowly; near the equivalence point a single drop makes a big jump.
Try this: Start with large drops and watch how fast the pH changes. Switch to small drops before the equivalence point.
Titrating unknown HCl
The beaker holds 20 mL of HCl with an unknown concentration c₁. Add the standard NaOH solution, c₂ = 0.1 mol/L, until the indicator changes colour sharply: that is the equivalence point, where n(NaOH) = n(HCl). From the volume V₂ you read off, c₁ = c₂·V₂ / V₁.
Try this: Find the jump roughly with large drops, then repeat the titration with small drops just before it. Only then guess c₁.
Weak vs strong acid
Both beakers hold 25 mL of acid at 0.1 mol/L. HCl is fully dissociated, CH₃COOH only slightly (Ka = 1.8·10⁻⁵), so it starts at a higher pH. During the titration acetic acid turns into acetate and the mixture acts as a buffer: pH = pKa + log([A⁻]/[HA]). At half-equivalence [A⁻] = [HA], so pH = pKa ≈ 4.74.
Try this: Choose CH₃COOH and add exactly 12.5 mL of NaOH. Read the pH and compare it with pKa. Then try the same with HCl.
Frequently asked questions
What is pH & Titration?
pH & Titration is a free interactive simulation from StudyFi Lab. It runs right in your browser, with no sign-up and nothing to install. Drip acid or base and watch the pH and the titration curve
Is pH & Titration free?
Yes. pH & Titration is completely free. It works in the browser on computers, tablets and phones, and you do not need an account.
What can I explore in pH & Titration?
Free mixing, Challenge: hit the pH, Titrating unknown HCl, Weak vs strong acid.
What does the “Free mixing” experiment show?
The beaker holds 50 mL of water with universal indicator. pH = −log[H⁺]: every drop of acid adds H⁺ ions, every drop of NaOH adds OH⁻ ions, which combine with H⁺ to form water. The scale is logarithmic, so ten times more H⁺ moves the pH by only 1. In water [H⁺]·[OH⁻] = 10⁻¹⁴.
What does the “Challenge: hit the pH” experiment show?
The beaker holds 50 mL of dilute acetic acid (pH about 3.2). Use drops of NaOH and acid to reach the target pH within ± 0.2. Acetic acid and acetate form a buffer, so around pH 4–6 the pH moves slowly; near the equivalence point a single drop makes a big jump.
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