Titration Curve Simulator Chemistry

Equivalence point: ---
Initial pH: ---
Current pH: ---
0.10
25
0.10
0.0
Drag the "Base added" slider to move along the titration curve. The current pH is displayed.

What is the Titration Curve Simulator?

Quick Answer: An interactive tool that plots pH versus volume of titrant added for acid-base titrations. Choose strong or weak acid/base combinations, adjust concentrations and volumes, and see the complete titration curve with equivalence point, buffer region, and indicator range highlighted. Understand neutralization and buffer concepts visually.

Theory of Acid-Base Titrations

The pH during a titration is determined by the reaction between acid and base. For a strong acid-strong base titration, the curve is steep near the equivalence point (pH = 7). For a weak acid-strong base (e.g., acetic acid + NaOH), the curve has a buffer region where pH changes slowly; the equivalence point is >7 due to the conjugate base. The simulator computes pH using the Henderson-Hasselbalch equation for buffer regions and direct formulas for excess H+ or OH−. The equivalence volume is Veq = (CacidVacid) / Cbase for monoprotic acids.

Step-by-Step Examples

Example 1: Strong Acid + Strong Base

  1. Select "Strong (HCl)" acid and "Strong (NaOH)" base. Set acid conc. 0.1 M, volume 25 mL, base conc. 0.1 M.
  2. Click "Draw Full Curve". The equivalence point is at 25 mL, pH = 7. Drag the base added slider to see a sharp pH jump near 25 mL.

Example 2: Weak Acid + Strong Base

  1. Choose "Weak (CH3COOH)" acid with Ka = 1.8×10-5 (pKa = 4.74). Keep base strong. Same concentrations.
  2. The curve shows an initial buffer region near pH = pKa when half-equivalence volume is added (12.5 mL). Equivalence point is at 25 mL, pH >7.

Example 3: Weak Acid + Weak Base

  1. Select both weak. The curve is less steep at equivalence point, making endpoint detection difficult with indicators. The simulator shows the gradual pH change.

Frequently Asked Questions

How is pH calculated?

For strong-strong: pH = -log[H+] or 14 + log[OH−]. For weak/strong mixtures, Henderson-Hasselbalch and ICE tables are used. Exact formulas are applied based on the region.

What is the equivalence point?

The point where stoichiometric amounts of acid and base have reacted. For strong-strong, pH = 7; for weak-strong, pH > 7; for strong-weak, pH < 7.

Can I see the buffer region?

Yes, in weak acid-strong base titrations, the pH remains relatively constant around pKa when base added is half the equivalence volume. The curve is colored differently in that region.

What indicators work for my titration?

The simulator doesn't display indicator ranges automatically, but the equivalence point pH is shown; choose an indicator with pKa near that pH (e.g., phenolphthalein for pH 8-10).

Can I enter custom Ka values?

For the weak acid, acetic acid (Ka = 1.8e-5) is used; for weak base, ammonia (Kb = 1.8e-5). Customizable Ka/Kb will be in a future update.