Determine whether or not each combination of substances can be used to create a buffer. 0.1 M HCl, 0.1 M KCl Choose... 0.1 M HNO2, 0.05 M NaOH Choose... 0.05 M HNO2, 0.05 M NaNO2 Choose... 1 M Na2HPO4, 1 M NaH2PO4 Choose... 0.4 M KOH, 0.2 M NaOH Choose...

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

not clear