ph problems and much more?

Question

For the reaction of hydrazine (N2H4) with water, Kb is 3.0 10-6. Calculate the pH of a 2.0 M solution of hydrazine.
H2NNH2(aq) + H2O(l) H2NNH3+(aq) + OH -(aq)

Answer 1

Formula:

Kb = (x)(x)/(2-x) approximately = x^2 divided by 2

x = OH = 2.45 x 10 ^ -3

so pOH = -log (2.45 x 10^-3) or 2.61

Therefore, pH = 14 -pOH or pH = 11.39

Answer 2

12