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Question 4
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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)
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Question 4 1 points Save Answer A solution is prepared at 25C that is initially 042 M in an X base a weak base with Kb74X104 and 042 M in conjugate acid HX Calc class=

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Answer:

pH = 10.87

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

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