Question

Hydrolysis of sodium acetate will give___
A. Acidic solution
B. Basic solution
C. Neutral solution
D. Normal solution

Answer 1

Hint: Sodium acetate is a salt of a weak acid and a strong base. It dissociates in water to form ions. Water itself is slightly dissociated into hydrogen ions (\[{H^ + }\]) and hydroxyl ions (\[O{H^ - }\]). These ions will react with the ionised sodium acetate. The relative concentration of the hydrogen and hydroxyl ions will decide the acidity/basicity of the solution.

Complete Step by Step Solution:
Sodium acetate (\[C{H_3}COONa\]) is formed by the neutralisation reaction of sodium hydroxide (\[NaOH\]) and acetic acid (\[C{H_3}COOH\]). It is thus the salt of a strong base and weak acid.
\[NaOH(aq) + C{H_3}COOH(aq) \to C{H_3}COONa(aq) + {H_2}O(aq)\]

On adding sodium acetate to water, it dissociates almost completely into its constituent ions. Think of this process as a “reverse neutralisation reaction”.
\[C{H_3}COONa(aq)
\rightleftharpoons C{H_3}CO{O^ - }(aq) + N{a^ + }(aq)\]
Pure water is always dissociated into hydrogen and hydroxyl ions to a very small extent as shown below:
\[{H_2}O(l) \rightleftharpoons {H^ + }(aq) + O{H^ - }(aq)\]
The concentrations of both ions are always equal in pure water (\[[{H^ + }] = [O{H^ - }]\]) and their product is always a constant which is called the ionic product of water. It is denoted as \[{K_w}\].
\[[{H^ + }][O{H^ - }] = {K_w}\] … (1)

When sodium acetate dissociates in water, the acetate ions take up some of the hydrogen ions furnished by water as shown below:
\[C{H_3}CO{O^ - }(aq) + {H^ + }(aq) \to C{H_3}COOH(aq)\]
This reduces the concentration of hydrogen ions. The undissociated water further dissociates to maintain the constant value of the ionic product of water (\[{K_w}\]) (see equation (1)). The newly furnished hydrogen ions are again taken up by the acetate ions as shown above. This leads to an increase in the relative concentration of the hydroxyl ions (\[O{H^ - }\]). The solution, therefore, becomes basic.

Thus, option B is correct.

Note: It is extremely important to remember that even pure water is always slightly dissociated into its constituent ions. Some students might consider pure water to be undissociated which is incorrect. Students might not be able to answer this type of question if they are unaware of this fact and do not know the concept of the ionic product of water.