Which of the following pairs constitutes a buffer?
- HCl and KCl
- HNO2 and NaNO2
- NaOH and NaCl
- HNO3 and NH4NO3
Answer
(2) HNO2 and NaNO2
Solution
As per NCERT, an acidic buffer is a mixture of a weak acid and its salt with a strong base (e.g. CH3COOH + CH3COONa).
HNO2 is a weak acid and NaNO2 is its salt with the strong base NaOH ⇒ buffer.
HCl + KCl and HNO3 + NH4NO3 contain a strong acid; NaOH + NaCl contains a strong base ⇒ not buffers.
Answer: (2)