Let's see another sample problem.

 This time you have a mixture of benzoic acid and p-methoxyphenol, dissolved in dichloromethane.

 How do you separate these two compounds?

Answer: You cannot use 5% NaOH to separate these two compounds. NaOH will react with both benzoic acid and p-methoxyphenol, thus both compounds will be extracted into the aqueous layer.

 Do you want to see what will happen with 5% NaOH?

Add 5% NaOH
Reset

 
See? Both compounds are extracted, so you cannot separate them with 5% NaOH. 

NaOH was too strong a base, thus it does not differentiate the strong and weak organic acids.
 
Use of weak inorganic base such as NaHCO3 will differentiate between the compounds.
 
Strong organic acids such as benzoic acid would be deprotonated and ionized, while weak organic acids such as phenols would NOT be deprotonated.
 
  
Add sat. NaHCO3
Reset
      
 
Did you see that you separated the two compounds using sat. NaHCO3 aqueous solution?
Let's continue then... 

Organic Web Chem University of Alberta