6) If you know the amounts of acid and base components in the buffer you can use

Question

6) If you know the amounts of acid and base components in the buffer you can use the equation to find the pH. Use the text to find the Ka for benzoic acid (C, H,COOH). Use the Henderson- Hasselbalch equation to find the pH of a buffer solution that is prepared with 100 mL of 0.10 M benzoic acid mixed with 100 mL of 0.10 M sodium benzoate (NaC, H,COO) solution (remember that sodium does not affect the pH so it is the benzoate that is the ion of interest) e uie smle, Instoad Rrdanh n 6. but 7) In the case when the stock concentrations of the acid and base components of the buffer are equal, the calculations become quite simple. Instead of using molarities in the equation, the volume of acid and base in mL can be used instead. Redo the calculation to question 6, but this time just use the volumes in mL and see that you get the same answer 8) We can adjust the pH of a buffer, within limits, to bring it to some desired value. For example, if Ka for the acid is 1.0 X10 and the amounts of acid and conjugate base are equal, the pH of the buffer solution would be 5.0. If we wish to make a buffer of pH equal to 4.5, we need to simply select volumes of the acid and conjugate base such that the ratio of [acid] to [base] would make 45 H,O1 equal to 10 or 3.2 X 10 M. So to make the desired buffer we could use 320 mL of 0.10 M acid and 100 mL of 0.10 M conjugate base. Show by calculation that these volumes will give you a buffer solution with pH of 4.5 9) For the same acid and base in (8), what ratio of volumes of acid and base would you need to get a pH of 5.5 Show your calculation. Give a set of volumes that satisfies the calculated ratio

Explanation / Answer

7. pH = pka + log([base]/[acid])

in this case pH = pKa + log ([C6H6COO-] / [C6H6COOH])

here the given concentrations of acid and base are same and pH =pKa

if we replace the conentration terms with volume.. there is in the calculated value for pH.

Related Questions

Navigate

• Browse (All)
• Browse 6
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.