Question

A 1.25g sample of a mixture of Na₂CO₃ and Na₂SO₄ is dissolved in 250mL solution. 25mL of this solution neutralises 20mL of 0.1NH₂SO₄. The % of Na₂CO₃ in the sample is:

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

Hint:

Only Na₂CO₃ reacts with acid; Na₂SO₄ is neutral.

Answer 1

The Correct Option is A

Step 1: Equivalents of acid: N₁V₁=N₂V₂ ⟹ 0.1×20= N×25 ⟹ N=0.08
Step 2: Total equivalents in 250 mL: 0.08×10=0.8
Step 3: Equivalent weight of Na₂CO₃ =53.
Step 4: Mass of Na₂CO₃ =0.8×53=0.848g
Step 5: Percentage: (0.848)/(1.25)×100=84.8%