Question

Question 4

1 points
Save Answer
A solution is prepared at 25°C that is initially 0.42 M in an "X" base, a weak base with Kb=7.4X10^-4, and 0.42 M in conjugate acid "HX". Calculate the pH of the
solution. Round your answer to 2 decimal places.
(Hint: pkw=pka + pkb)
A Moving to another question will save this response.
< Question 4 of 12>

Answer 1

pH = 10.87

Step-by-step explanation:

You can find pH of a buffer (Mixture of a weak base, X, and its conjugate acid, HX) by using H-H equation:

pH = pKa + log [X] / [HX]

pKb is -log Kb = 3.13

Using Hint pKw = pKa + pKb (pKw = 14)

pKw = pKa + pKb

14 - 3.13 = pKa

10.87 = pKa

Replacing in H-H equation:

pH = 10.87 + log [0.42M] / [0.42]

pH = 10.87 + log 1

pH = 10.87