Name _______________________________ Acid-Base pH Titration Tutorial Chem 178 Section __________

 If you need help in order to do a problem or activity, explain what you are doing to your TA. Your TA will listen and offer advice, but he or she will not tell you if you are right or wrong. Please turn in this tutorial to your TA when you are done. The acid-base titration computer simulation to accompany this tutorial is located on the 178 WebCT site or at URL: http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/stoichiometry/acid_base.html

 You can use another simulation to check your calculation for the initial pH of the acid solutions by going to : http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/acidbasepH/ph_meter.html

 For this tutorial you will compare the pH at various points during the titration of a strong acid vs. strong base to the pH at the same points during the titration of a weak acid vs. strong base. You need to do the calculations.

Activity 1. GOTO the computer simulation and select "Strong Acid vs. Strong Base". Click fill the buret with Base. Select HNO3 as the acid and KOH as the base. Select an indicator. The computer will automatically assign you a molarity for the acid and a volume for the acid.

A. Calculate the pH of the acid before any base is added.

 

 

B. Add 10.0 mL of the KOH. Write a chemical equation that illustrates what happens when HNO3 reacts with KOH.

 

 

C. Calculate the pH of the resultant solution, when you add 10.0 mL of the KOH. You will need to titrate to the end point in order to determine the molarity of the base (see D).

 

 

 

 

 

D. Titrate to the end point, calculate the molarity of the base, enter this number and click-on "OK". Then, go back and do part "C".

 

 

 

E. Click-on "graph". Make a sketch of this graph and indicate the following points: the initial pH of the acid, the point where 10 mL of KOH is added (and its pH) , the equivalence point (and its pH).

 

 

Activity 2. GOTO the computer simulation and select "Reset". Select "Weak Acid vs. Strong Base". Click fill the buret with Base. Select CH3COOH as the weak acid and KOH as the base. Select an indicator. The computer will automatically assign you a molarity for the acid and a volume for the acid.

F. Calculate the pH of the weak acid before any base is added.

 

 

G. Add 10.0 mL of the KOH. Write a chemical equation that illustrates what happens when CH3COOH reacts with KOH.

 

 

 

H. Calculate the pH of the resultant solution, when you add 10.0 mL of the KOH. You will need to titrate to the end point in order to determine the molarity of the base (see I). Also write an equation that illustrates what the equation is for the solution at this point in the titration.

 

 

 

I. Titrate to the end point, calculate the molarity of the base, enter this number and click-on "OK". Calculate the pH at the equivalence point. Then, go back and do part "H".

 

 

 

J. Click-on "graph". Make a sketch of this graph and indicate the following points: the initial pH of the acid, the point where 10 mL of KOH is added (and its pH) , the point on the graph where the pH = pKa, the equivalence point (and its pH).

 

 

 

 Activity 3. Compare the amount of 0.200 M KOH needed to neutralize 50.0 mL of 0.200 M HNO3 with the amount of 0.200 M KOH needed to neutralize 50.0 mL of 0.200 M CH3COOH. Is the volume of KOH more, less, or the same? Explain and or show.