Buffers And Acid-Base Titrations

 

The following problems are taken from T. L. Brown, H. E. Lemay, B. E. Bursten, & J. R. Burdge, Chemistry: The Central Science, Ninth Edition, Chapter 17. To see the solution to a problem or to return from the solution, click on the number of the problem.

 

14) (a) Calculate the pH of a buffer that is 0.100 M in NaHCO3 and 0.125 M in Na2CO3.

      (b) Calculate the pH of a solution formed by mixing 55 mL of 0.20 M NaHCO3 with 65 mL of 0.15 M Na2CO3.

               

16) A buffer is prepared by adding 5.0 g of ammonia (NH3) and 20.0 g of ammonium chloride (NH4Cl) to enough water to form 2.50 L of solution.

      (a) What is the pH of this buffer?

      (b) Write the complete ionic equation for the reaction that occurs when a few drops of nitric acid are added to the buffer.

      (c) Write the complete ionic equation for the reaction that occurs when a few drops of potassium hydroxide are added to the buffer.

 

18) How many grams of sodium lactate (NaC3H5O3) should be added to 1.00 L of 0.150 M lactic acid to form a buffer solution with pH 2.90? Assume that no volume change occurs when the NaC3H5O3 is added.

 

       
30) A 30.0-mL sample of 0.200 M KOH is titrated with 0.150 M HClO4 solution. Calculate the pH after the following volumes of acid have been added:

      (a) 30.0 mL

      (b) 39.5 mL

      (c) 39.9 mL

      (d) 40.0 mL

      (e) 40.1 mL

                   

32) Consider the titration of 30.0 mL of 0.030 M NH3 with 0.025 M HCl. Calculate the pH after the following volumes of titrant have been added:

      (a) 0 mL

      (b) 10.0 mL

      (c) 20.0 mL

      (d) 35.0 mL

      (e) 36.0 mL

      (f) 37.0 mL      


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