300 ❯ STEP 4. Review the Knowledge You Need to Score High
Measurements
You will be making measurements of volume and pH for a wide variety of substances. You
will be making graphs of pH versus mL of titrant added.Calculations
You can calculate the initial pH of a conjugate acid/base buffer by using the following
equations:[H+] = Ka [weak acid]/[conjugate base]; then pH = - log [H+]
If you want a buffer of a certain pH, then put in the Ka of the weak acid you want to use
and the [H+] desired and solve for the ratio of acid to base. If you have a choice of several
acid/base systems, then choose the one whose pKa is closest to the desired pH.Comments
Be extremely careful when working with the acids and bases and wear all of your personal
protective equipment, especially your goggles. When making dilutions, always add the acid
(or base) to water, NOT water to acid.❯ Common Mistakes to Avoid
- You measure initial and final values, but calculate the change.
- You use an analytical balance to weigh the mass (grams), but not the moles.
TIP