Which of the following mixture constitute a buffer?

Options

A. HCOOH+HCOONa
B. `Na_(2)CO_(3)+NaHCO_(3)`
C. NaCl+HCl
D. `NH_(4)Cl+(NH_(4))_(2)SO_(4)`

Answer

To determine which of the given mixtures constitute a buffer solution, we need to understand the definition of a buffer. A buffer solution is typically made up of a weak acid and its conjugate base, or a weak base and its conjugate acid.

Let’s analyze the mixtures one by one:

1. **HCOOF (Formic Acid and its Conjugate Base)**:
- HCOOF is a weak acid (formic acid). When it loses one H⁺ ion, it forms its conjugate base (HCOO⁻).
- Since we have a weak acid and its conjugate base present, this mixture constitutes a buffer solution.

2. **CO3²⁻ (Carbonate Ion)**:
- CO3²⁻ is the conjugate base of HCO3⁻ (bicarbonate), which is a weak acid. If we add H⁺ to CO3²⁻, it will form HCO3⁻.
- Therefore, this mixture also constitutes a buffer solution as it contains a weak base (CO3²⁻) and its conjugate acid (HCO3⁻).

3. **HCl and NaCl**:
- HCl is a strong acid and NaCl is a neutral salt. Strong acids do not have a conjugate base that can resist changes in pH.
- Therefore, this mixture does not constitute a buffer solution.

4. **NH4Cl (Ammonium Chloride)**:
- NH4Cl is a salt that dissociates into NH4⁺ (ammonium ion) and Cl⁻. NH4⁺ can act as a weak acid, but there is no weak base present to form a conjugate base.
- Therefore, this mixture does not constitute a buffer solution.

**Final Conclusion**: The mixtures that constitute a buffer solution are HCOOF and CO3²⁻.