For a solution that is 0.164 M NH3 and 0.102 M NH4Cl, calculate the [OH-]. NOTE: You may enter a number in scientific notation as: 6.6E-66 or 6.66*10^-66 or 6.66x10^-66 (DO NOT ADD Spaces)

Question

Can you pls assist in answering this question?

Answer 1

A solution of NH3 and NH4Cl represents a buffer solution since you have a weak base (NH3) and the conjugate acid (NH4+). We can use a form of the Henderson Hasselbalch equation to find the [OH-].

pOH = pKb + log [conj.acid] / [base]

Looking up the Kb for NH3, I find it to be 4.75

pOH = 4.75 + log 0.102/0.164

pOH = 4.75 + log 0.622

pOH = 4.75 + (-0.206)

pOH = 4.54

[OH-] = 1x10^-4.54

[OH-] = 2.88x10^-5 M