25.3 g of sodium carbonate 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,CO3^2- are respectively.......

Moles of Na₂CO₃  = mass/molar mass

  = 25.3/106

  = 0.239 moles

Molarity of Na₂CO₃ solution = number of moles/ volume in lire

   = 0.239/0.25  (250ml = 0.25 L)

  = 0.955 M

Now, 1 mole of Na₂CO₃ contains 2 moles of Na⁺ and 1 mole of CO₃^2- ions.

Therefore,

Concentration of Na⁺ = 2 x 0.955M = 1.91M

Concentration of CO₃^2-  = 1 x 0.955M = 0.955M