28 A solution is prepared by adding 100 mL of 15 MHC2H O2a t

28. A solution is prepared by adding 100 mL of 1.5 MHC2H O2a) to 100 mL of 1.5 MNaCH,O.(aq). The solution is stirred and its pH is measured to be 4.8. After 0.1 g NaOH(s) is added to the solution, and dissolved, the pH of the solution is measured and is still 4.8. Which of the following equations represents the chemical reaction that accounts for the fact that base was added but there was no detected change in pH? (A) H3O+(aq) + OH-(aq) 2 H2O() (B) OH-(aq) + Na +(aq) NaCl(s) (C) OH-(aq) + HC2H3O2(aq) C2H3O2-(aq) + H2O(/) (D) OH-(aq) + HC2H3O2(aq) H2CHLOs(aq) + H20(

Solution

Here The acetic acid and sodium acetate acts as a acidic buffer and ressists the change of pH when strong base or acid is added in solution.When a few drops of a base are added, the OH ions given by the base combine with the H₃O⁺ ions already present to form weakly ionized molecules of H₂O.As the solution is experiencing excess of OH^-,the buffer solution tries to nutrilize it through its acid.Here Acetic acid reacts with OH^- to give sodium acetate and water.

Hence the Option C is correct.