52E - Organic Chemistry (Mcmurry)

Question

Sodium bicarbonate, NaHCO₃, is the sodium salt of carbonic acid$\left({\mathbf{H}}_2{\mathbf{CO}}_3\right)$

 ,  $p{K}_a$=6.37. Which of the substances shown in Problem 2-44

will react significantly with sodium bicarbonate?

Step-by-Step Solution

Answer

Only acetic acid reacts with sodium bicarbonate. Acetic acid is the only substance in problem- 44 that is a stronger acid than carbonic acid.

Acid-Base reactions

Acids can donate protons, and bases are substances that can accept protons. Conjugate bases are formed from acids that have donated a proton, while conjugate acids are formed from bases that have accepted a proton.

Acid and bases are essential to many chemical processes, maintaining a stable internal environment in the human body, producing salt and water with the help of a neutralization process in which acid and base react to form a salt and water.

Relation between acidic strength and p K a values

Acid strengths are normally using  $p{K}_a$values rather than  values, where the  $p{K}_a$is the negative common logarithm of (acid dissociation constant):

 $\text{p}K\text{a = -log }{K}_a$

The stronger acid has a smaller $\mathbf{p}{K}_a$ , and a weaker acid has a larger  $\mathbf{p}{K}_a$

Identify the substance that reacts with Sodium bicarbonate

The substance with the largest value of pK_a is the least acidic.

Only acetic acid reacts with sodium bicarbonate. Acetic acid is the only substance in problem- 44 that is a stronger acid than carbonic acid. The  $p{K}_a$value of acetic acid ( = 4.76) is less than that of carbonic acid ( $p{K}_a$= 6.37). So the extent of the reaction is in a forward direction.

Hence the reaction of acetic acid with sodium bicarbonate is the only possible reaction in problem-44.

 $C{H}_{3}COOH+NaHC{O}_3\to C{H}_{3}COONa+H_{2}O+C{O}_2$

Acetic acid  Sodium        Sodium        water    Carbon

                                              Bicarbonate    acetate                    dioxide