Question

1. Calculate the pH of IL solution to which 5.OmL of 1.0 Macetic acid and 5.OmL of 0.5M sodium acetate have been added. The pKa of acetic acid is 4.76. 2. You need to carry out an enzymatic reaction at pH-3.5. A friend suggests phosphate buffer with pka of 7.21 as the basis of a buffer. Will this be a good choice to make the suitable buffer? Why or why not? 3. Calculate the concentration of acetate in a 100mM solution of acetic acid at pH 4.15. The pKa for acetic acid is 4.76. 4. Which species of phosphoric acid will predominate at pH value of (a) 1.5, (b) 4, (c) 9, and (d) 13. You would have to look for the pKa values for phosphoric acid.

Answer 1

1. Ans :- 4.46

Explanation :-

Acetic acid (CH₃COOH) is a weak acid and it form a buffer solution with its salt (CH₃COONa) of strong base that is its conjugate base CH₃COO^-. So, both will make acidic buffer solution and the pH of acidic buffer solution can be calculated by using the formula of Henderson-Hasselbalch equation :

pH = pK_a + log [Salt]/[Acid]

pH = pK_a of acetic acid + log [CH₃COONa] / [CH₃COOH]

pH = 4.76 + log 0.5 M / 1.0 M

pH = 4.76 - 0.3010

pH = 4.46

Hence, pH of the solution = 4.46