Carbonic Acid Is a Diprotic Acid,H₂CO₃,with K_a1 = 4

Multiple Choice

Carbonic acid is a diprotic acid,H₂CO₃,with K_a1 = 4.2 × 10^-7 and K_a2 = 4.8 × 10^-11 at 25°C.The ion product for water is K_w = 1.0 × 10^-14 at 25°C.What is the OH^- concentration of a solution that is 0.39 M in Na₂CO₃?

A) 9.0 × 10^-3 M
B) 2.1 × 10^-4 M
C) 9.6 × 10^-5 M
D) 4.3 × 10^-6 M
E) 4.0 × 10^-4 M