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A buffer is made by combining 0.05 mol of a sodium acetate,0.04 mol of acetic ac

ID: 681791 • Letter: A

Question

A buffer is made by combining 0.05 mol of a sodium acetate,0.04 mol of acetic acid and enough water to make a liter ofsolution.
a. What is the pH of this soltuion?
b. What is the pH after adding 0.01 mol of HCl to thebuffer?
c. What is the pH after adding 0.01 mol of NaOH to thebuffer? A buffer is made by combining 0.05 mol of a sodium acetate,0.04 mol of acetic acid and enough water to make a liter ofsolution.
a. What is the pH of this soltuion?
b. What is the pH after adding 0.01 mol of HCl to thebuffer?
c. What is the pH after adding 0.01 mol of NaOH to thebuffer?

Explanation / Answer

The pKa of acetic acid is 4.75 a) pH = pKa + log ([Base]/[Acid]) pH = 4.75 + log (0.05/0.04) pH = 4.85 b) [Base] = 0.05 - 0.01 = 0.04 [Acid] = 0.04 + 0.01 = 0.05 pH = pKa + log ([Base]/[Acid]) pH = 4.75 + log (0.04/0.05) pH = 4.65 c) [Base] = 0.05 + 0.01 = 0.06 [Acid] = 0.04 -0.01 = 0.03 pH = pKa + log ([Base]/[Acid]) pH = 4.75 + log (0.06/0.03) pH = 5.05 Hope this helps!