Explaining Resistance in pH of Buffer: Strong vs Weak Acids

In summary, the Henderson-Hasselbalch equation can be applied to strong acids, but not for calculating pH in the same way as for weak acids. The difference in buffer capacity between strong and weak acids is due to the inertness of weak acids and their ability to be easily forced into the solution, maintaining a stable pH. Strong acids can also resist pH changes, but in a different way. The Henderson-Hasselbalch equation cannot be used for calculating the pH of a buffer with a strong acid and its salt. Strong acids and bases are not typically used for making standard buffer solutions.
  • #1
Samurai33
13
0
could the equation - pH=pKa+log([A]/[HA]) - be applied for the case of strong acid? Although the percentage of dissociation of strong acid/base is very high, there still exists a equilibrium, right?

secondly, if i tried to explain the resistance in pH of buffer *in terms of* the above equation, then the pH of a buffer will depend only on the ratio of [A]/[HA]; then for both strong/weak acid with its salt, if i add H+ to each solution, the result will be: [A] decrease; [HA] increase (both cases). then how can i explain the difference that weak acid buffer has the ability to resist change in pH?

Please help me to solve this query, thanks a lot!
 
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  • #2
First question - Henderson-Hasselbalch equation works for strong acids too, although it can't be used for pH calculation, at least not in the same way as in the case of weak acids.

Second question is in fact about buffer capacity. Strong acids resist pH changes as well, although in slightly different way. In the case of strong acid pH changes only slightly in the case of relatively concentrated solutions, as neutralizing even 10% of acid doesn't change pH much. In the case of weak acids pH changes only slightly because weak acids are in a way inert - they almost don't dissociate on their own. Thus concentration of A- and HA can be easily forced on the solution, and as long as they don't change much, pH doesn't change as well.
 
  • #3
Borek said:
First question - Henderson-Hasselbalch equation works for strong acids too, although it can't be used for pH calculation, at least not in the same way as in the case of weak acids.
To be more specific, it cannot be used for calculating pH of buffer with strong acid and its salt??
 
  • #4
See the page mentioned (part about dichloroacetic acid).
 
  • #5
Samurai33 said:
To be more specific, it cannot be used for calculating pH of buffer with strong acid and its salt??

You don't need to use the H-H equation, also, strong acids/bases are not employed for making standard buffers.
 
  • #6
GCT said:
Ystrong acids/bases are not employed for making standard buffers.

How are you going to prepare pH = 1 buffer solution?
 

FAQ: Explaining Resistance in pH of Buffer: Strong vs Weak Acids

1. What is resistance in pH and how does it relate to buffer solutions?

Resistance in pH refers to the ability of a solution to maintain a relatively stable pH level even when small amounts of acid or base are added. In other words, it measures the ability of a buffer solution to resist changes in pH. Buffer solutions are made up of a weak acid and its conjugate base, and they work to maintain a stable pH by neutralizing any added acid or base.

2. Why are strong acids more effective at changing the pH of a buffer compared to weak acids?

Strong acids are more effective at changing the pH of a buffer because they completely dissociate in water, releasing a high concentration of hydrogen ions. This high concentration of hydrogen ions can quickly react with the conjugate base in the buffer, causing a more significant change in pH compared to weak acids, which only partially dissociate.

3. How does the concentration of the buffer components affect resistance in pH?

The concentration of the buffer components, specifically the weak acid and its conjugate base, directly affects resistance in pH. A higher concentration of these components will result in a more effective buffer, as there will be more molecules available to neutralize any added acid or base.

4. Can a buffer solution be resistant to both acids and bases?

Yes, a buffer solution can be resistant to both acids and bases. As long as the weak acid and its conjugate base are present in the buffer, they will work to neutralize any added acid or base, regardless of which one is added.

5. How can the strength of a buffer be measured?

The strength of a buffer can be measured by its buffering capacity, which is the amount of acid or base that can be added to the buffer before a significant change in pH occurs. A buffer with a high buffering capacity will be more resistant to changes in pH compared to a buffer with a low buffering capacity.

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