A buffer is made with sodium acetate (CH3COONa) and acetic acid (CH3COOH); the Ka for acetic acid is 1.80*10-5. The pH of the buffer is 3.98. What is the ratio of the equilibrium concentration of sodium acetate to that of acetic acid if you assume that the Henderson-Hasselbalch equation is accurate?

A. - 0.760

B. 0.174

C. 0.840

D. 5.75

E. Not enough information is given to answer this question.

Question

Dorian Allison

Chemistry

18 January, 00:07

A buffer is made with sodium acetate (CH3COONa) and acetic acid (CH3COOH); the Ka for acetic acid is 1.80*10-5. The pH of the buffer is 3.98. What is the ratio of the equilibrium concentration of sodium acetate to that of acetic acid if you assume that the Henderson-Hasselbalch equation is accurate?

A. - 0.760

B. 0.174

C. 0.840

D. 5.75

E. Not enough information is given to answer this question.

+1

Answers (1)

Know the Answer?

Abraham · Answer 1

B. 0.174

Explanation:

A buffer is formed by a weak acid (CH₃COOH) and its conjugate base (CH₃COO⁻, coming from sodium acetate). We can calculate the pH of this buffer using the Henderson-Hasselbalch equation.

pH = pKa + log [CH₃COO⁻]/[CH₃COOH]

pH - pKa = log [CH₃COO⁻]/[CH₃COOH]

3.98 - (-log 1.80 * 10⁻⁵) = log [CH₃COO⁻]/[CH₃COOH]

-0.760 = log [CH₃COO⁻]/[CH₃COOH]

[CH₃COO⁻]/[CH₃COOH] = anti log (-0.760)

[CH₃COO⁻]/[CH₃COOH] = 0.174