Q. 25.3 g of sodium carbonate, Na₂CO₃ is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, Na⁺ and carbonate ions, CO₃²⁻ are respectively (Molar mass of Na₂CO₃ = 106 g mol⁻¹)
A) 0.477 M and 0.477 M
B) 0.955 M and 1.910 M
C) 1.910 M and 0.955 M
D) 1.90 M and 1.910 M
Explanation
[Solution from source] Moles = 25.3/106 = 0.2387 mol in 0.250 L, so [Na₂CO₃] = 0.955 M. Each formula unit gives 2 Na⁺ and 1 CO₃²⁻, so [Na⁺] = 1.910 M and [CO₃²⁻] = 0.955 M. The reversed pair swaps the ions. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.