Question looking for hydroxide ion concentration?

Question

The [OH-] concentration of a solution of 3.41 mol/L sodium carbonate is?

a.bcd? mol/L

Answer 1

Sodium carbonate = Na₂CO₃

In solution, Na₂CO₃ dissociates into 2Na⁺ and CO₃^2-

The carbonate anion then undergoes hydrolysis as follows:

CO₃^2- + H₂O ==> HCO₃^- + OH^- and the Kb for CO32- is 2.1x10^-4

Kb = 2.1x10^-4 = [HCO3-][OH-]/[CO₃^2-] = (x)(x)/3.41- x = x²/3.41 (neglect x in denominator as it is small)

x² = 7.2x10^-4

x = [OH-] = 2.7x10^-2 M