Final answer:
Options C (1 M NH3 and 1.5 M NH4+) and D (1 M HF and 1 M F-) represent viable buffer solutions because they consist of a weak base and its conjugate acid or a weak acid and its conjugate base at sufficient concentrations to maintain pH.
Step-by-step explanation:
A viable buffer solution is one that consists of a weak acid and its conjugate base or a weak base and its conjugate acid. The purpose of a buffer is to resist changes in pH when small quantities of acid or base are added. Looking at the options given, we can identify which ones can form effective buffers.
- A. 1 M HF and 0.0001 M F-: This is a mixture of a weak acid (hydrofluoric acid) and its conjugate base (fluoride ions), but the concentration of F- is much lower than the HF, which might not be effective for buffering.
- B. 1 M HCl and 1 M Cl-: Hydrochloric acid is a strong acid, and a strong acid cannot form a buffer with its conjugate base because it fully dissociates in water.
- C. 1 M NH3 and 1.5 M NH4+: This mixture consists of a weak base (ammonia) and its conjugate acid (ammonium ion), and can form a viable buffer solution, as the concentrations are close enough to maintain the pH.
- D. 1 M HF and 1 M F-: This is a mixture of a weak acid and its conjugate base in equal concentrations, which is ideal for creating a buffer solution.
Therefore, options C and D are viable buffer solutions.