Weak Acids and Bases
Textbook problems that can be checked using the Virtual Lab

1. (2pts) You have two bottles, one filled with 1M HAc (HAc = acetic acid) and one filled with 1M NaOH. You want to make 100ml of a buffer with pH=4.6 by mixing together appropriate amounts of these solutions. How much of each solution do you use? 2. (2pts) You have two bottles, one filled with 1M NaAc (NaAc = sodium acetate) and one filled with 1M HCl.You want to make 100ml of a buffer with pH=5.2 by mixing together appropriate amounts of these solutions. How much of each solution do you use? 3. (2pts) Methyl red has two forms, a red form at low pH and a yellow form at high pH (see Figure 10.8 of the Oxtoby textbook). You add 75ml of 1.0M NaClO to 50ml of 1.0M HClO. You add a drop of indicator solution containing methyl red (you can ignore dilution effects due to the addition of the drop). What is the color of the solution? What is the ratio between the concentration of the red and yellow forms of methyl red ([red form]/[yellow form])? 4. (2pts) The following shows the results of titrating 50ml of a diprotic weak acid with 0.100M KOH. a) Based on the above titration curve, what are pK1 and pK2 for this acid? b) Based on the above titration curve, what is the concentration of the acid in this solution? c) When 25ml of KOH have been added, what is the ratio [HA-]/[H2A]? d) When 75ml of KOH have been added, what is the ratio [HA-]/[H2A]?