5. Which of the two solutions below has a higher buffering capacity? Explain why

Question

5. Which of the two solutions below has a higher buffering capacity? Explain why one solution has a better ability to resist changes in pH. (Hint: Consider what makes a good buffer and pay special attention to the arrows used in the reactions.) Solution A: This solution is prepared by combining equal amounts of a weak acid with its conjugate base, resulting in the expression below: Solution B: This solution is prepared by combining equal amounts of a strong acid with its conjugate base, resulting in the expression below: HA(aq) + H2O(l) A(aq) +H30'(aq) HX(aq) + H2O(l) X(aq) +H3O+(aq)

Explanation / Answer

Solution A will have higher buffer capacity. A good buffer should be able to resist the change in pH for a narrow range.

Generally, the buffer is created by mixing a strong acid with its weak conjugate base or a weak base with a strong conjugate acid.

The solution B won't be a good buffer as the reaction is not in equilibrium.

If the Hydronium( H3O+) ions are increased in concentration then it won't be able to go in the backward direction as the reaction is not favored in the reverse direction. So this buffer will be only good when it is exposed to a base.

Also after sometime the salt concentration will also become huge and it will not be able to resist the change in pH to a narrow range. The pH change will take place in non-ideal range (i.e more than 3 units change)

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