Question

1.25 g of a sample of Na₂CO₃ and Na₂SO₄ is dissolved in 250mL solution. 25mL of this solution neutralizes 20mL of 0.1NH₂SO₄. The percentage of Na₂CO₃ in the sample is:

• A. \(84.8\%\)
• B. \(8.48\%\)
• C. \(15.2\%\)
• D. 42.4%

Hint:

In mixed salt problems: • Identify the reacting species • Use equivalents directly for neutralization

Answer 1

The Correct Option is A

Step 1: Normality relation: N₁V₁=N₂V₂ Nbase×25 = 0.1×20 ⟹ Nbase=0.08
Step 2: Total equivalents in 250mL: 0.08×(250)/(1000)=0.02
Step 3: Only Na₂CO₃ reacts. Equivalent weight of Na₂CO₃=53. Mass of Na₂CO₃=0.02×53=1.06g
Step 4: Percentage: (1.06)/(1.25)×100=84.8%