Buffer Capacity
Introduced| English | Meaning |
|---|---|
| buffer capacity/ˈbʌfə kəˈpæsɪti/ | buffer capacity |
How much can it take?
- Every protector has a limit before it gives out.
- A dilute mixture tires quickly; a concentrated one holds firm.
- Its reserves decide how much shock it can absorb.
- Beyond that limit, the pH finally lurches.
The reserve strength
- Buffer capacity 缓冲容量 is how much acid or base a buffer can absorb.
- A higher capacity resists larger additions.
- Exceed it, and the pH swings sharply.
Once a buffer's capacity is exceeded, the pH changes sharply.
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The buffer fails and can no longer resist the change.
More concentrated, more capacity
- Higher concentrations of both components give a larger capacity.
- More reserve means more added acid or base can be neutralized.
- Dilute buffers run out quickly.
A more concentrated buffer has a...
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More of both components means more can be absorbed.
A dilute buffer can absorb more added acid than a concentrated one.
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False. A dilute buffer has fewer moles of acid and base in reserve, so it is overwhelmed sooner.
Buffer capacity increases with the ____ of the buffer components.
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Higher concentrations provide more reserve.
Balanced is best
- Capacity is greatest when acid and base are about equal.
- A lopsided buffer runs out on one side first.
- So near $\text{pH} = \text{p}K_a$, the capacity peaks.
Buffer capacity is greatest when the ratio of acid to base is about...
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A balanced 1:1 buffer handles both directions best.
Which buffer resists more added acid: $1.0\ \text{M}$ or $0.01\ \text{M}$ (same ratio)?
- The $1.0\ \text{M}$ buffer has far more reserve.
- So it resists more added acid — a higher capacity.
What raises buffer capacity?
Sort each buffer by whether it resists more or less added acid/base.
Two buffers have the same pH. Do they necessarily have the same capacity?
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Same pH (ratio) can hide very different concentrations.
Buffer capacity is about the amount of buffer (its concentration), not just the ratio — two buffers can share a pH but have very different capacities. It peaks at a 1:1 ratio ($\text{pH} = \text{p}K_a$). And once the capacity is exceeded, the buffer fails and the pH jumps.
Buffer capacity is how much acid or base a buffer can absorb before failing. It rises with the concentration of both components and peaks when they are balanced ($\text{pH} = \text{p}K_a$). Two buffers can share a pH yet differ greatly in capacity.