In an acid-base titration, 0.1 M HCl solution was added to the NaOH solution of unknown strength. Which of the…
Ionic Equilibrium · Class 11 · JEE Main Previous Year Question
In an acid-base titration, 0.1 M HCl solution was added to the NaOH solution of unknown strength. Which of the following correctly shows the change of pH of the titration mixture in this experiment?
- a✓
- b
- c
- d
Step 1 — Identify the titration: Strong acid (HCl) added to strong base (NaOH).
Step 2 — Expected pH curve:
- Initially: NaOH solution high pH (≈ 12-13)
- As HCl is added: pH decreases gradually
- Near equivalence point: pH drops sharply (from ≈ 10 to ≈ 4)
- After equivalence point: excess HCl pH levels off at low value (≈ 1-2)
Step 3 — Correct graph: The correct graph shows:
- Start at high pH
- Gradual decrease
- Sharp drop at equivalence point
- Levels off at low pH
This is the classic strong acid into strong base titration curve — starts high, drops sharply at equivalence, ends low.
Answer: Option (1) — Graph A (starts high, drops sharply, levels off at low pH)
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