Required Procedure Go to the Acetate Buffer Experiment. Select 4 250-mL Erlenmey
ID: 1017268 • Letter: R
Question
Required Procedure
Go to the Acetate Buffer Experiment.
Select 4 250-mL Erlenmeyer Flasks from the pictorial or equipment menu. Keep track of which one is which.
Click on the first flask and add 100 mL of distilled water to it. Click on the second flask and add 100 mL of distilled water to it.
Click on the third flask and add 74.0 mL of 0.1 M acetic acid to it. Also add 1.1 g of sodium acetate to the third flask. Finally add 26.0 mL of distilled water to the third flask. Stir the solution.
Click on the fourth flask and add 74.0 mL of 0.1 M acetic acid to it. Also add 1.1 g of sodium acetate to the fourth flask. Finally add 26.0 mL of distilled water to the fourth flask. Stir the solution.
Right click on each of the flasks and choose pH meter. The pH of each solution should appear in blue below the flask.
Record the pH of each solution on a separate WORD document.
Add 5.0 mL of HCl to the first flask. Record the pH on the Report sheet.
Add 5.0 mL of NaOH to the second flask. Record the pH on the Report sheet.
Add 5.0 mL of HCl to the third flask. Record the pH on the Report sheet.
Add 5.0 mL of NaOH to the fourth flask. Record the pH on the Report sheet.
Write equations for the reactions taking place in each of the flasks. For an equilibrium arrow ( ) is an equals sign (=) (Unless you know how to do equilibrium arrows). Unless you know how to do subscripts and superscripts, use H2O for water, A- for acetate ion, HA for acetic acid, H+ for hydrogen ion, H3O+ for hydronium ion, Na+ for sodium ion, and OH- for hydroxide ion.
Reaction in flask 1
Reaction in flask 2
Reaction in flask 3.
Reaction in flask 4.
Explanation / Answer
#1 flask
Initial pH = 7
After adding 5 ml HCl
Reaction : H2O + H+ <==> H3O+
#2 Flask
Initial pH = 7
After adding 5 ml NaOH
Reaction : H2O + OH- <==> H2O + OH-
#3 Flask
Initial pH
[HA] = 0.1 M x 74 ml/100 ml = 0.074 M
[A-] = 1.1 g/82.03 g/mol x 0.100 L = 0.134 M
pH = pKa + log(base/acid)
= 4.74 + log(0.134/0.074) = 5.00
After adding 5 ml HCl
Reaction,
A- + H+ <==> HA
#4 Flask
Initial pH
[HA] = 0.1 M x 74 ml/100 ml = 0.074 M
[A-] = 1.1 g/82.03 g/mol x 0.100 L = 0.134 M
pH = pKa + log(base/acid)
= 4.74 + log(0.134/0.074) = 5.00
After adding 5 ml NaOH
Reaction : HA + OH- <==> A- + H2O
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