1. What is the pH of a buffer that is composed of 100. mL of 0.20 M NH 4 Cl and

Question

1. What is the pH of a buffer that is composed of 100. mL of 0.20 M NH4Cl and 200. mL of 0.10 M NH3?

2. If an acetic acid/sodium acetate buffer solution is prepared from 100.0 mL of 0.100 M acetic acid, what volume of 0.100 M sodium acetate must be added to yield a final pH of 4.00?

3. How many mL of 12.0 M HCl must be added to 500.0 ml of 0.50 M sodium acetate to prepare a buffer of pH 4.75?

4. How many grams of ammonium chloride must be dissolved in 1.00 L of 0.200 M ammonia to make a buffer of pH 8.50?

5. Which of the following would be an ideal buffer solution?

0.20 M HCN / 0.10 M KCN                                 0.20 M HCl / 0.10 M KOH

0.20 M CH3CO2H / 0.10 M HCO2H                    0.10 HCl / 0.010 M KCl

Describe how to prepare 500.0 ml of this buffer with maximum buffering capacity.

Explanation / Answer

CH3COOH is a weak acid - calculate [H+] from the Ka equation for question a)
When you add NaOH to the acid you produce a buffer solution Use the Henderson Hasselbalch equation
At the half equivalence point , pH = pKa . pKa for the acid is 4.77 . The half equivalence point is c) So the pH here will be 4.77

I will leave you to rework the problem . If you have not made any progress , or someone else has not done the work for you , I will come back to this problem tomorrow.
Edit next day:
No progress from you and no other answer: So we will do this in full
Question a) You have a weak acid. In order to calculate pH you first have to determine the [H+] in the solution. You do this using the Ka equation:

Ka = [H+] [CH3COO-] / [CH3COOH]
You know that [H+] = [CH3COO-] so for product we write [H+]

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

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