Print calculator Periodic Table Question 10 of 15 Sapling Learning this question

Question

Print calculator Periodic Table Question 10 of 15 Sapling Learning this question was writonby ken ahantharmortriat underwooduriversty You are given a buffer that contains a weak base whose concentration is 0.450 M and its acid whose concentration is 0.200 M. The volume of this solution is 0.450 L, lf0.080 L of an HCI solution with a concentration of 1.10 M is added to this solution, what will the pH of the combined solution be? The pKa of the weak acid is 4.12. Number pH ® Give s view solution Check Answer Next SExit

Explanation / Answer

wak base = 0.45

conjugate acid = 0.2

V= 0.45 L

mol of weak base = MV = 0.45*0.45 = 0.2025

mol of conjugate = MV = 0.45*0.2 = 0.09

now, after adding acid:

V = 0.08 L of HCl and M = 1.1 M is added

mol of HCL = MV = 0.08*1.1 = 0.088 mol of HCl

so

after reactions (i.e. acid reacts with base and forms conjguate)

mol of weak base = 0.2025-0.088 = 0.1145

mol of conjugate = 0.09+0.088 = 0.178

the ratio :

pH = 4.12 + log(0.178/0.1145) = 4.3116

final pH = 4.3116

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