Which pairs of compounds are capable of making a buffer? Select all that apply.

• A. 1.3 M LiOH and 1.7 M HCOOH
• B. 0.784 M NH4+ and 0.800 M HClO4
• C. 0.35 M CH3CO2H and 0.35 M NaOH
• D. 0.80 HNO3 and 0.15 MgO

Answer: (A)

Verified step by step guidance

1. Understand what a buffer solution is: A buffer solution is a system that minimizes pH changes when small amounts of acid or base are added. It typically consists of a weak acid and its conjugate base, or a weak base and its conjugate acid.
2. Examine each combination to determine if it forms a buffer: A buffer is formed when there is a weak acid and its conjugate base or a weak base and its conjugate acid present in the solution.
3. Analyze the first combination, HC2H3O2 and KC2H3O2: HC2H3O2 is acetic acid (a weak acid) and KC2H3O2 is potassium acetate (the conjugate base of acetic acid). This combination forms a buffer.
4. Analyze the second combination, H2SO3 and NaHSO3: H2SO3 is sulfurous acid (a weak acid) and NaHSO3 is sodium bisulfite (the conjugate base of sulfurous acid). This combination forms a buffer.
5. Analyze the fourth combination, HNO3 and KNO3: HNO3 is nitric acid (a strong acid) and KNO3 is potassium nitrate (a salt that does not provide a conjugate base of a weak acid). This combination does not form a buffer because it involves a strong acid and lacks a weak acid-conjugate base pair.