g a pH Buffer In this experiment, each group will make a different pH buffer at
ID: 704990 • Letter: G
Question
g a pH Buffer In this experiment, each group will make a different pH buffer at an assigned pH Your assigned pH value is your group number plus 2 (i.e., group 4 will make a buffer at pH 6). You must select an appropriate buffering compound to maintain that pH. The following compounds will be present on the front table for you to choose from. TABLE 2.1 Compounds Present on Front Table. pk 4.76 10.4 7.5 MW (grams/mol) 136.08 221.32 238.30 119.98 121.14 210.10 Compound Sodium acetate CAPS HEPES Sodium phosphate 2.15/6.82/12.38 Tris Citric acicd 8.1 3.06/4.74/6.40 The pK, and formula weight for each compound is given on the bottle. Phosphate and citric acid both have three pK, values, one for each H that can dissociate. In selecting your buffering compound, choose one that will allow you to get to your target pH most efficiently, with addition of the least amount of HCl or NaOH. For example, don't use citric acid to make a buffer at pH 5 or 6 (why?). Once you haveExplanation / Answer
You should use CAPS
A buffer is combination of a weak acid and its conjucate base or a weak acid and its conjucate acid
the pH of a buffer solution is given by the following formula which is called Henderson-Hasselbalch equation
pH = pKa + log([A-] /[HA])
where,
HA = weak acid
A- = conjucate base
If you choose your compount with pKa value close to your target pH value, you can maintain the [A-] /[HA] ratio near to 1 which give good buffer capacity.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.