Preparing Buffer Solutions: Calculating the Number of Grams ofConjugate Base Needed
Use the table of K values given with this problem to choose thebest weak acid to start from for making a buffer that holds the pHof the solution at 3.20. Make your selection so that you maximizethe capacity of the buffer.
You select a 200.0 ml volumetric flask to which you add 54.00 mL ofa 2.90 M solution of the weak acid you just selected. To finishpreparing your buffer you must now add the sodium salt of theconjugate base. How many grams of the sodium salt of your conjugatebase must you add so that when you finally fill the flask to themark with deionized water the buffer will have a pH of 3.20.
| Weak Acid | Ka |
| CH3COOH (Acetic Acid) | 1.8 X 10-5 |
| C6H5COOH (Benzoic Acid) | 6.5 X 10-5 |
| CH3CH2CH2COOH (ButanoicAcid) | 1.5 X 10-5 |
| HCOOH (Formic Acid) | 1.8 X 10-4 |
| HBrO (Hypobromous Acid) | 2.8 X 10-9 |
| HNO2 (Nitrous Acid) | 4.6 X 10-4 |
| HClO (Hypochlorous Acid) | 2.9 X 10-8 |
| CH3CH2COOH (Propanoic Acid) | 1.3 X 10-5 |
| HCN (Hydrocyanic Acid) | 4.9 X 10-10 |
I posted this question before and they got the answer of 8.00gwhich is NOT CORRECT, so I was looking someone else to help me withthis.
