Conjugate pairs versus not conjugate pairs

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In summary, to make a 25mM buffer with pH 5.2, you can add 25mM ethanoic acid and 25mM sodium ethanoate. This will result in a buffer solution with a concentration of 25mM even after adjusting the pH. However, if you use 25mM Tris-base and 25mM phosphoric acid, which is not a conjugate pair, you will not get a buffer with a concentration of 25mM after adjusting the pH to 5.2. This is because buffer solutions require a conjugate pair to maintain their concentration through the common ion effect.
  • #1
sotellme
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to make a 25mM buffer with pH5.2 i add 25mM ethanoic acid with 25mM sodium ethanoate. after adjusting the pH, the buffer will still be 25mM.

will this also be the case if i use 25 mM Tris-base and 25 mM phosphoric acid? will i still get a buffer with 25mM after adjusting the pH to 5.2 with the phosphoric acid?

the first one is a conjugate pair (ethanoic acid and sodium ethanoate), while the second one is not a conjugate pair (Tris-base and phosphoric acid)

thanks.
 
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  • #2
No. You'll need a conjugate pair for a buffer solution, although I'm not sure if your method complies with any other existing ways to make a buffer.

Buffers solutions exists through common ion effect, this is why for the most part the concentration of the conjugates do not undergo equilibrium; I believe that it may be an entropical phenomenon, somebody correct me if I'm mistaken.
 
  • #3


Yes, the buffer will still be 25mM after adjusting the pH with phosphoric acid. However, the resulting buffer will not be as effective as the conjugate pair buffer made with ethanoic acid and sodium ethanoate. This is because conjugate pairs have the ability to resist changes in pH more effectively compared to non-conjugate pairs. Therefore, if there are any changes in the environment or addition of other compounds, the conjugate pair buffer will maintain its pH and buffering capacity better. Non-conjugate pair buffers, on the other hand, may experience changes in pH and lose their buffering capacity more easily. So, while both buffers will still have a concentration of 25mM, the conjugate pair buffer will be more reliable in maintaining its desired pH.
 

1. What are conjugate pairs in chemistry?

Conjugate pairs in chemistry refer to two substances that are related by the gain or loss of a proton. The first substance is called the conjugate acid, as it has gained a proton, while the second substance is called the conjugate base, as it has lost a proton.

2. What is the significance of conjugate pairs in chemical reactions?

Conjugate pairs are important in chemical reactions because they allow substances to act as both acids and bases, making them amphoteric. This means they can donate or accept protons, allowing for a variety of reactions to occur.

3. Is it necessary for conjugate pairs to have the same chemical formula?

No, conjugate pairs do not necessarily have the same chemical formula. They may have different charges and may differ in the number of protons, but they are related through the transfer of a proton.

4. How do you identify conjugate pairs in a chemical equation?

To identify conjugate pairs in a chemical equation, look for substances that differ by one proton and have opposite charges. For example, in the equation HCl + H2O ⇌ H3O+ + Cl-, the conjugate pairs are HCl and Cl- and H2O and H3O+.

5. Can a substance be its own conjugate pair?

Yes, a substance can be its own conjugate pair if it can both donate and accept protons. These substances are called amphiprotic and include water and ammonia.

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