Question

There are three different ways to make a buffer. Which of the following is NOT one of the methods?

Select one:

a. Adding equal amounts of a strong acid and a strong base

b. Adding comparable amounts of the weak acid and its conjugate base to water

c. Adding a limited amount of strong acid to a solution of weak base

d. Adding a limited amount of strong base to a solution of weak acid

Answer 1

Buffers are the solution that resist in change the pH of the solution when small amounts of a strong acid or a strong base are added. For example : A solution of acetic acid and sodium acetate (CH3COOH + CH3COONa) is an example of a buffer.

If we add hydrochloric acid, most of the hydronium ions from the hydrochloric acid combine with acetate ions, forming acetic acid molecules hence concentraion change of hydronium ion will remain the same. On the other hand if we add NaOH, hydroxide ions react with the few hydronium ions present to form water this will further react with acetic acid to form acteate ion hence base concentration will also does not affect

Three ways to prepare buffer are:

1.      Weak acid and its salt e.g: CH3COOH + CH3COONa
2.      Weak acid and strong base e.g. CH₃COOH + Na⁺ + OH^-  ⟶  CH₃COONa + H₂O
3.      Salt of weak base and strong acid e.g. CH₃COO^-+ HCl  ⟶  CH₃COOH + Cl^-

so adding equal amount of strong acid and strong base will not give buffer solution, further it will lead to neutralization reaction resulting in salt formation for example HCl+NaOH will give NaCl as salt