Question

Hydrazine, N2H4, is a weak base and is used as fuel in the space shuttle.
N2H4(aq)+H2O(l)âN2H5+(aq)+OHâ(aq)

Part A

If the pH of a 0.133 M solution is 10.66, what is the ionization constant of the base?

Express your answer using two significant figures.

Answer 1

Answer:

Kb = 1.6*10^-6

Explanation:

The given reaction is:

$N2H4(aq)+H2O(l)\rightarrow N2H5+(aq)+OH-(aq)$

The ionization constant of the base Kb is given as:

$Kb = \frac{[N2H5+][OH-]}{[N2H4]}------(1)$

The pH = 10.66

therefore, pOH = 14-pH = 14-10.66 =3.34

$[OH-] = 10^{-pOH} =10^{-3.34} =4.57*10^{-4} M$

[N2H5+] = [OH-] = 4.57*10^-4M

[N2H4] = 0.133 M

Based on eq(1)

$Kb = \frac{[4.57*10^{-4}]^{2}}{[0.133]}=1.6*10^{-6}$