Answer:
Explanation:
A buffer solution is a mixture of two substances consisting of a weak acid and it's conjugate base. A buffer solution resists a change in pH.
From the description above, we can denote that a buffer must consist of a weak acid and it's conjugate base/salt.
The first option has a strong acid (HCl) and hence the solution cannot form a buffer.
The second option has a strong base (NaOH) which is not a conjugate base of HNO₂. Thus the solution cannot form a buffer.
The third option has HNO₂ which is a weak acid and NaNO₂ which is it's salt, hence it can form a buffer.
The fourth option has NaH₂PO₄ which will act as an acid while Na₂HPO₄ will act as it's salt to produce a phosphate buffer.
The fifth option has two strong bases hence cannot form a buffer
