Problem: Calculate the pH of a 0.20 M solution of sodium benzoate (NaC6H5COO) given that the Ka of benzoic acid (C6H5COOH) is 6.50 x 10-5.

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FREE Expert Solution

We are being asked to calculate the pH for a 0.20 M solution of NaC6H5COO. 


NaC6H5COO is the salt form of the conjugate base of C6H5COOH.


NaC6H5COO disociates as: 

NaC6H5COO(aq) → Na+(aq) + C6H5COO-(aq)


The acid dissociation goes as: 

C6H5COOH(aq) + H2O(l) → C6H5COO-(aq) + H3O+(aq)



Since we’re dealing with a weak base we will have to create an ICE chart to determine the equilibrium concentration of each species:

C6H5COO-(aq)  weak baseproton acceptor
H2O → will act as the weak acidproton donor


Equilibrium reaction:        C6H5COO-(aq)  + H2O(l)    C6H5COOH(aq) + OH-(aq)


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Problem Details

Calculate the pH of a 0.20 M solution of sodium benzoate (NaC6H5COO) given that the Ka of benzoic acid (C6H5COOH) is 6.50 x 10-5.

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Weak Bases concept. If you need more Weak Bases practice, you can also practice Weak Bases practice problems.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Cruz's class at USF.