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Equilibrium appeared 36 times across 3 years — 4.2% of Chemistry. This question is from Buffer Solutions.

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The pH of an aqueous solution containing 1M benzoic acid (pKₐ = 4.20) and 1M sodium benzoate is 4.5. The volume of benzoic acid solution in 300 mL of this buffer solution is ______ mL.

Numerical Answer Type:
Enter a numerical value Answer: 100 to 100 +4 marks

Solution & Explanation

Related Formula

Henderson-Hasselbalch Equation for Acidic Buffers:

pH = pKₐ + ( [Salt][Acid] )
Core Logic

Let the volume of 1M Benzoic acid be Vₐ mL and the volume of 1M Sodium benzoate be Vₛ mL. Total volume = Vₛ + Vₐ = 300 mL.

Millimoles of acid = 1 × Vₐ = Vₐ Millimoles of salt = 1 × Vₛ = Vₛ

Applying Henderson's Equation:

4.5 = 4.2 + ((Vₛ)/(Vₐ))
Step 1: Calculate Volume Ratio
((Vₛ)/(Vₐ)) = 4.5 - 4.2 = 0.3

Since 2 ≈ 0.3, we have:

(Vₛ)/(Vₐ) = 2

Vₛ = 2 Vₐ

Step 2: Substitute and Solve

We know Vₛ + Vₐ = 300 Substituting Vₛ = 2 Vₐ:

2 Vₐ + Vₐ = 300

3 Vₐ = 300

Vₐ = 100 mL
Chapter Mix

Class 11 Chemistry: Equilibrium

Reference Study Guides

Equilibrium

More Equilibrium Previous-Year Questions — Page 8

Q62 jee_main_2024_31_jan_morning Equilibrium Constant
For the given reaction, choose the correct expression of KC from the following :- Fe(aq)³⁺ + SCN(aq)⁻ leftharpoons (FeSCN)(aq)²⁺
  • A. KC = [FeSCN²⁺][Fe³⁺][SCN⁻]
  • B. KC = [Fe³⁺][SCN⁻][FeSCN²⁺]
  • C. KC = [FeSCN²⁺][Fe³⁺]²[SCN⁻]²
  • D. KC = [FeSCN²⁺]²[Fe³⁺][SCN⁻]

Solution

Related Formula
KC = [Products][Reactants]
Core Logic
KC = Products ion conc.Reactants ion conc. KC = [FeSCN²⁺][Fe³⁺][SCN⁻]
Chapter Mix

Class 11 Chemistry: Equilibrium

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