객관식
Consider a buffer solution that is 0.50 M in NH3 and 0.20 M in NH4Cl. For ammonia, pKb = 4.75. Calculate the pH of 1.0 L of the solution upon addition of 0.010 mol of solid NaOH to the original buffer solution.
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18. Aqueous Equilibrium
Henderson-Hasselbalch Equation
Multiple Choice
What is the [CH3CO2-]/[CH3CO2H] ratio necessary to make a buffer solution with a pH of 4.44? Ka = 1.8 × 10^-5 for CH3CO2H.
A
1.78
B
0.56
C
1.00
D
2.50
검증된 단계별 안내1
Identify the components of the buffer solution: acetic acid (CH3CO2H) and its conjugate base, acetate ion (CH3CO2-).
Use the Henderson-Hasselbalch equation to relate the pH of the buffer solution to the concentrations of the acid and its conjugate base: \( \text{pH} = \text{pKa} + \log \left( \frac{[\text{CH}_3\text{CO}_2^-]}{[\text{CH}_3\text{CO}_2\text{H}]} \right) \).
Calculate the pKa from the given Ka value: \( \text{pKa} = -\log(1.8 \times 10^{-5}) \).
Substitute the given pH (4.44) and the calculated pKa into the Henderson-Hasselbalch equation to solve for the ratio \( \frac{[\text{CH}_3\text{CO}_2^-]}{[\text{CH}_3\text{CO}_2\text{H}]} \).
Rearrange the equation to isolate the ratio: \( \frac{[\text{CH}_3\text{CO}_2^-]}{[\text{CH}_3\text{CO}_2\text{H}]} = 10^{(\text{pH} - \text{pKa})} \).
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