For these types of questions I am having trouble understanding why we solve for
ID: 716754 • Letter: F
Question
For these types of questions I am having trouble understanding why we solve for a or b. This is the solution that the professor posted. I know that a is the weak acid and b is the weak base of the buffer. But what I dont understand is that if the buffer is at pKa 7.21 and we want a pH of 7.6, why dont we solve for the weak base to add OH to increase the pH? Also where did the 1.289 come from? I thought it was 0.289 mol H+
PH 7.Lo 6. (8 pts.) You want to study the oxygen binding ability of hemoglobin at pH 7.60. Youdecide to use a phosphate buffer. How would you make up 500 ml of 50 mM phosphate buffer, pH 721, starting with 1.00 M K3PO4 and either 10.0 M HCl or 10.0 M NaOH? The pKa's of phosphoric acid are 2.12,7.21, and 12.32. Show all calculations. 2.1 7.2 -2 12.32 stant here ul cL 289 we neel 24uiv (o.soo 2)(o.oso M phmphatao.025 5(oo5 ).322 0.025 naR ,1799)0.6322 noe x = 3.22 X=25 m plus H20 to 50D lExplanation / Answer
This is because concentration of acid and base will decide the pH of the buffer solution .and buffer is not at pKa 7.21 this is the pka value of acid whose pka value is always taken near the pH value. From the values of concern.of acid and base we will calculate miles of both and from there we will calculate required volume to prepare buffer solution of given pH.
And 1.289 is mistaken accrual concentration is 0.289