Select all the correct statements about a buffer.

It contains a strong acid and the salt of its conjugate base.
It contains a weak acid and the salt of its conjugate base.
It contains a strong base and the salt of its conjugate acid.
It contains a weak base and the salt of its conjugate acid.
It resists changes in pH when small amounts of acid or base are added.

Question

Select all the correct statements about a buffer.

It contains a strong acid and the salt of its conjugate base.
It contains a weak acid and the salt of its conjugate base.
It contains a strong base and the salt of its conjugate acid.
It contains a weak base and the salt of its conjugate acid.
It resists changes in pH when small amounts of acid or base are added.

BlackTom AI · Accepted Answer

Question restatement: Select all the correct statements about a buffer.

Option 1: It contains a strong acid and the salt of its conjugate base.
- This is incorrect. A buffer does not rely on a strong acid; strong acids fully dissociate and do not provide the equilibrium system needed for buffering. Buffers typically involve a weak acid and its conjugate base or a weak base and its conjugate acid.

Option 2: It contains a weak acid and the salt of its conjugate base.
- This is correct. A classic buffer solution is made from a weak acid (which partially dissociates) and the salt of its conjugate base, which helps resist pH changes by shifting equilibria when small amounts of H+ or OH- are added.

Option 3: It contains a strong base and the salt of its conjugate acid.
- This is incorrect. Using a strong base would drastically alter the pH and would not establish the necessary equilibrium to buffer effectively. Buffers rely on equilibria between a weak species and its conjugate form, not on strong, fully dissociated species.

Option 4: It contains a weak base and the salt of its conjugate acid.
- This is correct. A buffer can also be formed from a weak base and the salt of its conjugate acid (the conjugate acid salt). This system resists pH change by the base–acid conjugate pair buffering added protons or hydroxide ions.

Option 5: It resists changes in pH when small amounts of acid or base are added.
- This is correct. The defining property of a buffer is its ability to resist pH changes under small additions of acid or base due to the equilibrium between the weak acid/base and its conjugate form.

Putting it together: The statements that are true are 2, 4, and 5, which correspond to the classic buffer behavior and composition described above. Therefore, the option that lists 2, 4, and 5 as the correct statements is the accurate choice.

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