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CW Acid and Bases 6
± Core Chemistry Skill: Calculating the pH of a Basic Buffer
3 of 3
Review
|Constants|Periodic Table
Introduction
A buffer consists of a weak acid or base, and the conjugate of that acid or base.
Consider a buffer made by combining the weak base B
with its conjugate acid, BH+
:

B(aq)+H2O(l)⇌BH+(aq)+OH−(aq)

Kb=[BH+][OH−][B]

The OH−
concentration of this buffer can be calculated using the Kb
expression:
[OH−]=Kb[B][BH+]

Part A
An ammonia/ammonium buffer solution contains 0.15 M
NH3
and 0.61 M
NH4+
. The Kb
value of ammonia is 1.8×10−5
. Calculate the pH
of this buffer.
Express the pH numerically.
View Available Hint(s)for Part A
Activate to select the appropriates template from the following choices. Operate up and down arrow for selection and press enter to choose the input value typeActivate to select the appropriates symbol from the following choices. Operate up and down arrow for selection and press enter to choose the input value type

pH
=
nothing
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