Question

Select ALL of the following combinations that will form a buffer solution.

a. H2CO3 and NaHCO3
b. NH4Cl and NH3
c. NaNO3 and HNO3
d. 50 mL 0.10 M NaOH + 25 mL 0.10 M CH3CO2H (acetic acid)

Answer 1

A buffer solution is formed from a weak acid or weak base and its conjugate salt. The combinations that will form a buffer solution from the given options are:
`H_(2)CO_(3)`
`NaHCO_3`l and
`NH_3`, and the mixture of NaOH and
`CH_3CO_2H`, options a , b & d are correct answers.

Step-by-step explanation:

To determine which combinations will form a buffer solution, we need to look for a mix of a weak acid or weak base with its conjugate salt. A buffer solution can resist changes in pH when small amounts of acid or base are added. Here are the combinations in question:

• 
  `H_(2)CO_(3)` and
  `NaHCO_3` (sodium bicarbonate) - This pair consists of a weak acid and the salt of its conjugate base, which makes it a buffer solution.
• 
  `NH_4CI` (ammonium chloride) and
  `NH_3` (ammonia) -
  `NH_4CI` is a salt of the weak base
  `NH_3`, hence this combination can also form a buffer.
• 
  `NaNO_3` (sodium nitrate) and
  `HNO_3` (nitric acid) - Nitric acid is a strong acid and its salt will not form a buffer with it.
• 50 mL 0.10 M NaOH (a strong base) + 25 mL 0.10 M
  `CH_3CO_2H` (acetic acid) - By combining a weak acid with a portion of its conjugate base formed through partial neutralization by NaOH, this mixture can indeed form a buffer.

The combination of
`H_(2)CO_(3)`
`NaHCO_3`, NH4Cl and
`NH_3`, and the mixture of NaOH and
`CH_3CO_2H` in appropriate proportions all represent buffer systems. Hence, options a , b & d are correct answers.