Sodium benzoate (c6h5coona), the sodium salt of the weak acid benzoic acid, is used as a food preservative. a solution is prepared by dissolving 0.100 mol of sodium benzoate in enough pure water to produce 1.00 l of solution. if the pka for benzoic acid is 4.20, calculate the ph of the sodium benzoate solution.

8.6

Explanation:

Using the expression :

Where, is the dissociation constant of water.

At ,

Thus, for benzoic acid , pKa = 4.20

Thus,

for Sodium benzoate can be calculated as:

The benzoate ion will dissociate as:-

expression is:-

Given that:-

Moles = 0.100 moles

Volume = 1.00 L

Thus, Concentration = 0.100/ 1.00 M = 0.1 M

Considering the ICE table in the image below.

So,

Solving for x, we get that,

Thus,

Also,

Also, pH + pOH = 14  

So, pH = 14 - 5.4 = 8.6

a