SK015 Chapter 7 Acidic Buffer

Acidic Buffer Solutions

Introduction of buffer solution

Identify acidic buffer

Explanation acidic buffer

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 HNO₂ was 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]