Multiple Choice
A buffer solution is made by combining a weak acid with its conjugate salt. What will happen to the pH if the solution is diluted to one-fourth of its original concentration?
18. Aqueous Equilibrium
Intro to Buffers
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What is the pH of a 1.0 L buffer solution containing 0.500 M HF and 0.300 M NaF. Ka for HF = 3.5 × 10−4.
A
0.30
B
1.88
C
2.00
D
3.24
E
3.46
Verified step by step guidance1
Identify the components of the buffer solution: HF (weak acid) and NaF (its conjugate base, F⁻).
Use the Henderson-Hasselbalch equation to find the pH of the buffer solution: \( \text{pH} = \text{pKa} + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right) \).
Calculate the pKa from the given Ka value for HF: \( \text{pKa} = -\log(\text{Ka}) \). Substitute \( \text{Ka} = 3.5 \times 10^{-4} \) into the equation.
Substitute the concentrations of the acid and its conjugate base into the Henderson-Hasselbalch equation: \( [\text{HA}] = 0.500 \text{ M} \) and \( [\text{A}^-] = 0.300 \text{ M} \).
Calculate the pH using the values obtained from the previous steps.
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