Which one of the following pairs of 0.100 mol L-1 solutions, when mixed, will produce a buffer solution?

A. 50. mL of aqueous CH3COOH and 25. mL of aqueous CH3COONa
B. 50. mL of aqueous CH3COOH and 25. mL of aqueous HCl
C. 50. mL of aqueous NaOH and 25. mL of aqueous HCl
D. 50. mL of aqueous CH3COOH and 100. mL of aqueous NaOH
E. 50. mL of aqueous CH3COONa and 25. mL of aqueous NaOH

Technically, a weak acid/salt of the weak acid (or weak base/salt of the weak base) produces a buffered solution. Technically, again, with no concns listed in the answers, none of them will do. However, I think, in the spirit of the problem, that is understood to be equal concns of the mixture in A through E.

A will do it.
B is not a buffer but it has some buffering action versus acid. Adding a base makes a buffer.
C. NO.
D. No.
E. No.

A. 50 mL of aqueous CH3COOH and 25 mL of aqueous CH3COONa.

Why? Because they are both sources of acetic acid and its conjugate base, acetate. You need these two components to create a buffer solution.
Just like mixing a self-deprecating joke with a confident punchline, these two solutions will come together to balance each other out! It's like comedy chemistry!

To identify which pair of solutions will produce a buffer solution, we need to check if the pair consists of a weak acid and its conjugate base or a weak base and its conjugate acid.

A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added. It consists of a weak acid and its conjugate base, or a weak base and its conjugate acid.

Let's analyze the options:

A. 50 mL of aqueous CH3COOH and 25 mL of aqueous CH3COONa
This pair consists of acetic acid (CH3COOH) and sodium acetate (CH3COONa), which is the conjugate base of acetic acid. Therefore, this pair can form a buffer solution.

B. 50 mL of aqueous CH3COOH and 25 mL of aqueous HCl
This pair consists of acetic acid (CH3COOH) and hydrochloric acid (HCl), which is not the conjugate base of acetic acid. Therefore, this pair cannot form a buffer solution.

C. 50 mL of aqueous NaOH and 25 mL of aqueous HCl
This pair consists of sodium hydroxide (NaOH) and hydrochloric acid (HCl), neither of which is a weak acid or its conjugate base. Therefore, this pair cannot form a buffer solution.

D. 50 mL of aqueous CH3COOH and 100 mL of aqueous NaOH
This pair consists of acetic acid (CH3COOH) and sodium hydroxide (NaOH), which is not the conjugate base of acetic acid. Therefore, this pair cannot form a buffer solution.

E. 50 mL of aqueous CH3COONa and 25 mL of aqueous NaOH
This pair consists of sodium acetate (CH3COONa) and sodium hydroxide (NaOH), neither of which is a weak acid or its conjugate base. Therefore, this pair cannot form a buffer solution.

Based on this analysis, the pair of 50 mL of aqueous CH3COOH and 25 mL of aqueous CH3COONa (Option A) will produce a buffer solution.

To determine which pair of solutions will produce a buffer solution, we need to understand what a buffer solution is.

A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added to it. It is composed of a weak acid and its conjugate base (or a weak base and its conjugate acid) in approximately equal concentrations.

In this case, we have various pairs of solutions to choose from. Let's analyze each option:

A. 50 mL of aqueous CH3COOH and 25 mL of aqueous CH3COONa: This pair consists of acetic acid (CH3COOH) and its sodium salt (CH3COONa). Acetic acid is a weak acid and its conjugate base, the acetate ion (CH3COO-), is a weak base. These compounds are suitable for a buffer solution.

B. 50 mL of aqueous CH3COOH and 25 mL of aqueous HCl: This pair includes acetic acid and hydrochloric acid (HCl). HCl is a strong acid, so this combination does not meet the criteria for a buffer solution.

C. 50 mL of aqueous NaOH and 25 mL of aqueous HCl: This pair involves sodium hydroxide (NaOH) and hydrochloric acid. Both NaOH and HCl are strong electrolytes, so this combination does not form a buffer solution.

D. 50 mL of aqueous CH3COOH and 100 mL of aqueous NaOH: This pair includes acetic acid and sodium hydroxide. While acetic acid can act as a weak acid in a buffer solution, the excess of NaOH (strong base) would make it difficult for this pair to function as a buffer solution.

E. 50 mL of aqueous CH3COONa and 25 mL of aqueous NaOH: This pair consists of sodium acetate (CH3COONa) and sodium hydroxide. Both compounds are salts and do not possess the necessary weak acid/base properties required for a buffer solution.

Therefore, the correct answer is Option A: 50 mL of aqueous CH3COOH and 25 mL of aqueous CH3COONa.