Acidic Buffer Solutions

Example 1 (acidic buffer)

A student is asked to prepare a buffer solution at pH 4.6 using 50.00 mL of 0.5 M benzoic acid, C6H5COOH and sodium benzoate, C6H5COONa. 

  • Calculate the mass of sodium benzoate required to prepare the buffer solution.

  • Explain the buffering effect of adding a small amount of NaOH and HCl, respectively into the buffer solution.

[Ka (C6H5COOH) = 6.5 x 10-5 ]   


Example 2 (Buffer that form after titrations between weak acid and strong base)

Name the processes that occur when HNO2 solution is added separately into water, NaOH solution and NaNO2 solution. Write the chemical equation for each process.


In three separate beakers, 20.0 mL of 0.08 M HNOwas added to 40.0 mL of water, 40.0 mL of 0.03 M NaOH and 40.0 mL of 0.03 M NaNO2, respectively. Determine the pH of the solution in each beaker.

[Ka for HNO2 = 4.5 x 10-4]

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