Acid-Base Titration & Indicator Virtual Lab

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Acid-Base Titration & Indicators Virtual Lab

JEE & NEET Concepts Mastering Suite

Interactive Sandbox Enabled www.chemca.in

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1. Select Titration System

Titration Type Strong Acid vs Strong Base (HCl vs NaOH) Weak Acid vs Strong Base (CH₃COOH vs NaOH) Strong Acid vs Weak Base (HCl vs NH₄OH)

In Burette (Titrant) NaOH (0.1 M)

In Flask (Analyte) HCl (0.1 M, 25.0 mL)

Indicator Option

Select an indicator to observe the endpoint.

Burette Reading 0.00 mL

Live pH Meter 1.00

0 mL─

10─

20─

30─

40─

50─

OFF

HCl + No Indicator

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2. Titration Curve

pH vs V(mL)

Equivalence Pt: 25.00 mL

Phenol Range (8.2 - 10.0) Methyl Orange Range (3.1 - 4.4)

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3. Interactive Litmus Station

Test the flask's chemical nature at any point of the titration by dipping a litmus strip.

Observations will be logged here once a test is initiated.

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JEE/NEET High Yield

Indicator Principle: Weak organic acids or bases that change color based on their ionization state:

HIn ⇌ H⁺ + In⁻

Selecting the Right Indicator: The pH range of the indicator must fall within the steep vertical section of the titration curve.

🟢 Strong Acid - Strong Base: pH steep jump is 3 to 11. Use Phenolphthalein or Methyl Orange.

🔴 Weak Acid - Strong Base: pH jump is 7 to 11. pH at equivalence > 7. Use Phenolphthalein.

🔵 Strong Acid - Weak Base: pH jump is 3 to 7. pH at equivalence < 7. Use Methyl Orange.

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Equivalent Solver

Solve $N_1V_1 = N_2V_2$ for acid-base equivalence logic. Leave one field blank to solve.

N₁ (Acid)

V₁ (Acid, mL)

N₂ (Base)

V₂ (Base, mL)

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JEE/NEET Quick Quiz

Score: 0/5

📖 Deep Dive: Concept of Salt Hydrolysis & Indicator Transition (JEE/NEET Level)

Mathematical Hydrolysis Formulae

When a Weak Acid is titrated with a Strong Base, at the equivalence point, the solution contains only basic salt which undergoes anionic hydrolysis:

pH = 7 + ½ pKₐ + ½ log C

Conversely, for a Strong Acid with a Weak Base at the equivalence point, cationic hydrolysis occurs yielding an acidic solution:

pH = 7 - ½ pK_b - ½ log C

Phenolphthalein (pH 8.2 - 10.0)

Phenolphthalein (HPh) is colorless in acidic form and turns deep pink in basic form (Ph⁻) due to extended resonance conjugation.

• At pH < 8.2: Concentration of un-ionized [HPh] is high (Colorless).
• At pH > 10: Concentration of ionized [Ph⁻] is high (Pink).
• For WA vs SB titrations, this is perfect as the pH leaps drastically through this range.

Methyl Orange (pH 3.1 - 4.4)

Methyl Orange (MeOH) changes from red in acidic media to yellow in basic/neutral environments.

• At pH < 3.1: Exists in quinonoid structure (Red).
• At pH > 4.4: Exists as azo compound (Yellow).
• For SA vs WB titrations, the pH drops rapidly within the acidic range making Methyl Orange the ideal choice.

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