MAny common weak bases are derivatives of NH3, where one or more of the hydrogen

Question

MAny common weak bases are derivatives of NH3, where one or more of the hydrogen atoms have been replaced by another substituent. Such reaction can be generically symbolized as NX3(aq)+H2O(l)-->HNX3(aq)+OH^-(aq) where NX3 is the base and HNX3 is the conjugate acid. The equilibrium-constant expression for this reaction is

Kb=[HNX3^+][OH^-]/[NX3] where Kb is the base ionization constant.

PART A

1.) If Kb for NX3 is 5.0*10^-6, what is the pOH of a 0.175 M aqueous solution of NX3?

pOH=

2.) If Kb for NX3 is 5.0*10^-6, what is the percent ionization of a 0.325 M aqueous solution of NX3?

Explanation / Answer

1)let the iosisation of NX3 be x.so,

5*10^-6=x^2/(0.175-x)

or x=9.33*10^-4

so [OH-]=9.33*10^-4

so pOH=3.03

b)let the degree of dissociation be k.so,

5*10^-6=0.325k^2/(1-k)

or k=0.003915

so the %ionisation=0.003915*100

=0.3915 %

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