Question

Which of the following is a buffer solution?
\[
  A.{\text{ }}C{H_3}COOH + C{H_3}COONa \\
  B.{\text{ }}NaCl + NaOH \\
  C.{\text{ }}HCl + N{H_4}Cl \\
  D.{\text{ }}C{H_3}COOH + HCl \\ \]

Answer 1

Hint- In order to solve the given problem first we will understand the basic meaning of buffer solution also we will study about the characteristics of buffer solution and what are the uses of a buffer solution. Further we will study about the preparation of the buffer solution and find out which of the given options is a buffer solution.

Complete answer:
First let us understand the basic definition of a buffer solution.
> A buffer solution (pH buffer or hydrogen ion buffer, more precisely) is an aqueous solution composed of a combination or a mixture of a neutral or a very weak acid and its conjugate base, or vice versa.
> A buffer solution is a solution which only changes slightly when adding an acid or base to it. It consists of a weak-acid and its conjugate base for an acid-buffer solution. It consists of a weak-base and its conjugate acid for a basic-buffer solution.
> The main purpose of a buffer solution is simply to resist the pH change so that if we add an acid or base into it, the pH of the solution won't be much affected. The acid or base applied is neutralized.
> Now let us check for the buffer solution amongst the given options.
- Amongst the given four options; only option A and option D contains acetic acid \[C{H_3}COOH\] which is a weak acid. Option B has sodium chloride which is not an acid and option C has hydrochloric acid, which is a strong acid. So we have to now look into option A and option D.
- As the other part of option D is hydrochloric acid which is a strong acid and not a salt of weak acetic acid so option D does not have a buffer solution.
As option A contains \[C{H_3}COOH + C{H_3}COONa\] which is a mixture of acetic acid \[C{H_3}COOH\] , which is a weak acid and sodium acetate \[C{H_3}COONa\] which is the salt of weak acid.
Hence, \[C{H_3}COOH + C{H_3}COONa\] is a buffer solution.So, option A is the correct option.

Note- Acidic buffer solutions are generally made from a weak acid and one of its salts-often a salt of sodium. A common example of this would be a solution combination of ethanoic acid and sodium ethanoate. Basic buffer has a simple pH, and is primed with strong acid by adding a weak base and water. A combination of ammonium hydroxide and ammonium chloride is an example of an alkaline buffering solution.