Table of contents

1. Chemical Measurements1h 50m
2. Tools of the Trade1h 17m
3. Experimental Error1h 52m
4 & 5. Statistics, Quality Assurance and Calibration Methods1h 57m
6. Chemical Equilibrium3h 41m
7. Activity and the Systematic Treatment of Equilibrium1h 0m
8. Monoprotic Acid-Base Equilibria1h 53m
9. Polyprotic Acid-Base Equilibria2h 17m
10. Acid-Base Titrations2h 37m
11. EDTA Titrations1h 34m
12. Advanced Topics in Equilibrium1h 16m
13. Fundamentals of Electrochemistry2h 19m
14. Electrodes and Potentiometry41m
15. Redox Titrations1h 14m
16. Electroanalytical Techniques57m
17. Fundamentals of Spectrophotometry50m

9. Polyprotic Acid-Base Equilibria

Diprotic Buffers

Analytical Chemistry

9. Polyprotic Acid-Base Equilibria

Diprotic Buffers

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Multiple Choice

Calculate the pH of a solution made by mixing 8.627 g of sodium butanoate in enough 0.452 M butanoic acid, HC₄H₇O₂, to make 250.0 mL of solution. K_a = 1.5 x 10^-5.

4.82

4.98

5.85

4.66

4.06

Verified step by step guidance

First, calculate the moles of sodium butanoate (NaC4H7O2) using its molar mass. The molar mass of sodium butanoate is approximately 110.09 g/mol. Use the formula: moles = mass (g) / molar mass (g/mol).

Next, determine the concentration of sodium butanoate in the solution. Since the total volume of the solution is 250.0 mL (or 0.250 L), use the formula: concentration (M) = moles / volume (L).

Now, calculate the initial concentration of butanoic acid (HC4H7O2) in the solution. The concentration is given as 0.452 M.

Use the Henderson-Hasselbalch equation to find the pH of the buffer solution. The equation is: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base (sodium butanoate) and [HA] is the concentration of the acid (butanoic acid).

Calculate the pKa from the given Ka value using the formula: pKa = -log(Ka). Substitute the values into the Henderson-Hasselbalch equation to find the pH of the solution.