A 0505 G Sample of a Monoprotic Base (Mm = 45

A 0.505 g sample of a monoprotic base (mm = 45.09 g/mol) was dissolved in water to produce 100.0 mL of solution with a pH = 11.84. What is the ionization constant of this base?

A) 4.3 × 10^-5
B) 1.9 × 10^-23
C) 4.3 × 10^-4
D) 3.4 × 10^-1
E) 1.3 × 10^-11