Choosing the Right Indicator for a Titration

🎯 Choosing the Right Titration Indicator

💡 Key Rule: Pick an indicator whose color change range matches the titration's equivalence point pH.

🎨 Match the indicator pKa (or transition range) to the steep vertical part of the pH curve.

✅ Titration Type & Best Indicator

• Strong acid + strong base → pH 7 → use phenolphthalein or bromothymol blue
• Strong acid + weak base → pH < 7 → use methyl orange
• Weak acid + strong base → pH > 7 → use phenolphthalein
• Weak acid + weak base → no sharp change → no good indicator!

🧠 Quick Check

Which indicator would be best for titrating HCl with NaOH?

⚡ Indicator Range Hints

Phenolphthalein: 8.3–10 (colorless to pink)
Methyl orange: 3.1–4.4 (red to yellow)
Bromothymol blue: 6.0–7.6 (yellow to blue)

🎯 Target Practice

You're titrating acetic acid (weak) with NaOH (strong). Which indicator?

✏️ Match the endpoint pH to the indicator’s range. No sharp jump = no clear color change!