Multiple Choice
Which of the following combinations can result in the formation of a buffer?
18. Aqueous Equilibrium
Intro to Buffers
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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?
A
The pH will increase.
B
The pH will decrease.
C
The pH will remain constant.
D
The solution will become more neutral.
Verified step by step guidance1
Understand the concept of a buffer solution: A buffer solution is composed of a weak acid and its conjugate base (or a weak base and its conjugate acid). It resists changes in pH when small amounts of acid or base are added.
Recognize the role of dilution in buffer solutions: Diluting a buffer solution decreases the concentration of both the weak acid and its conjugate base equally.
Apply the Henderson-Hasselbalch equation: The equation \( \text{pH} = \text{pK}_a + \log \left( \frac{[\text{A}^-]}{[\text{HA}]} \right) \) shows that the pH depends on the ratio of the concentrations of the conjugate base \([\text{A}^-]\) and the weak acid \([\text{HA}]\).
Analyze the effect of dilution: When a buffer solution is diluted, the concentrations of \([\text{A}^-]\) and \([\text{HA}]\) decrease equally, so their ratio \( \frac{[\text{A}^-]}{[\text{HA}]} \) remains constant.
Conclude the effect on pH: Since the ratio \( \frac{[\text{A}^-]}{[\text{HA}]} \) does not change, the pH of the buffer solution remains constant upon dilution.
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