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Calculate the pH of a buffer solution made by adding 15.0 g anhydrous sodium acetate (NaC2H3O2) to 100.0 mL of 0.200 M acetic acid. Assume there is no change in volume on adding the salt to the acid. (pKa for acetic acid is 4.74 or Ka is 1.8 x 10-5)3.

Answer :

Answer:

pH of Buffer Solution 5.69

Explanation:

Mole of anhydrous sodium acetate = [tex]\frac{Given mass}{Molecular mass}[/tex]

                                                           = [tex]\frac{15}{82}[/tex]

                                                           = 0.18 mole

 100 ml of 0.2 molar acetic acid  means

= M x V

= 0.2 x 100

= 20 mmol

= 0.02 mole

Using Henderson equation to find pH of Buffer solution

pH = pKa + log[tex]\frac{[Salt]}{[Acid]}[/tex]

     = 4.74 + log[tex]\frac{0.18}{0.02}[/tex]

     = 4.74 + log 9

     = 5.69

So pH of the Buffer solution = 5.69

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