Experiment: Acids and Bases


    This JAVA applet is designed to help you to define and solve acid/base equilibrium problems. Select a weak acid (acetic acid, Ka = 1.8E-5; nitrous acid, Ka = 4.0E-4) or base (ammonia, Kb = 1.8E-5) from the first pop-up menu and enter desired volume in mL (volume <= 100 mL) in the box to the right. If you select "None" in the pop-up menu, then enter 0 mL for the volume. Next, select a salt from the list (sodium acetate, ammonium chloride, or sodium nitrite) in the second pop-up menu and enter the volume in the box to the right. If you select "None", then enter 0 mL for the volume. Finally, select "None," HCl, or NaOH from the third pop-menu and enter the desired volume in mL in the box to the right. Enter 0 mL if you select "None." Click the "pH" button to initiate the animation. At the end of the animation a few drops of a Universal indicator are added to the solution. Use the color chart on the right to obtain the approximate pH of the solution. To repeat the experiment or begin a new experiment, click the "Reset" button and follow the same procedure.

    After you have mixed the solutions, added the indicator, and obtained an approximate pH, use the techniques discussed in class to calculate the pH. To check your calculated pH or to obtain help with the calculation, click the "Help" button. A second window will appear. Enter the initial molarities - the values found in the Initial row of the ICE Table - of the weak acid or base, the salt, and HCl or NaOH; the value of the equilibrium constant; and your calculated pH. Next click the "Enter" button. Confirmation of the correct pH or suggestions for calculating the correct pH are displayed. If your pH is incorrect, use the suggestions and recalculate the pH. To check the recalculated pH click the "Clear" button, enter the new values, and then click the "Enter" button. Continue in this manner until you have computed the correct pH.

    Use the applet to define and solve the following problems. Calculate the pH (with correct number of significant digits ) of the solution in each problem. Try the Tutorial for Experiment: Acids and Bases for suggestions and help.

  1. Add 25 mL of the 0.20 M nitrous acid solution to the beaker and calculate the pH of the solution.
  2. Add 50 mL of the 0.20 M nitrous acid solution and 50 mL of the 0.30 M sodium nitrite solution to the beaker. Calculate the pH of the solution in the beaker.
  3. Add 25 mL of the 0.50 M sodium acetate solution to the beaker and calculate the pH.
  4. Add 50 mL of 0.50 M sodium acetate solution and 50 mL of 0.10 M HCl solution to the beaker. Calculate the pH of the solution.
  5. Add 25 mL of 0.50 M acetic acid solution, 25 mL of 0.50 M sodium acetate solution, and 100 mL of 0.10 M HCl solution to the beaker. Calculate the pH of the solution.
  6. Add 25 mL of the 0.20 M nitrous acid solution, 15 mL of 0.30 M sodium nitrite solution, and 60 mL of 0.10 M NaOH solution to the beaker. Calculate the pH of the solution.

    If you have defined, solved, and submitted for credit Problems #1, # 2, and #3, then you may check the solutions to Acid-Base Problem #2 and Problem #3

    If you have defined, solved, and submitted for credit Problems #4, # 5, and #6, then you may check the solutions to Acid-Base Problem #4 , Problem #5 , and Problem #6



Nutt 99




Dr. Nutt's CHE 115 Course