Problem: What mass of sodium benzoate should be added to 160.0 mL of a 0.16 M benzoic acid solution in order to obtain a buffer with a pH of 4.30?

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We have to calculate how much sodium benzoate should be added to 160.0 mL of a 0.16 M benzoic acid solution in order to obtain a buffer with a pH of 4.30.


Benzoic acid is a weak acid with a chemical formula of C6H5CO2H. It ionizes partially into its solution.

C6H5CO2H(aq) + H2O(l) C6H5CO2-(aq) + H3O+(aq)


Sodium benzoate is a soluble salt and dissociates into solution to form sodium ions (Na+) and benzoate ions (C6H5CO2-).

Recall: Alkali metal salts are water-soluble.

NaC6H5CO2(aq) → Na+(aq) + C6H5CO2-(aq)

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What mass of sodium benzoate should be added to 160.0 mL of a 0.16 M benzoic acid solution in order to obtain a buffer with a pH of 4.30?

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