Question

Which of the following mixtures would result in a buffered solution when 1.0 L of each of the two solutions are mixed?
a. 0.2 M HNO3and 0.4 M NaNO3
b. 0.2 M HNO3and 0.4 M HF
c. 0.2 M HNO3and 0.4 M NaF
d. 0.2 M HNO3 and 0.4 M NaOH

Short answer

Answer

The correct option is C. The mixture in option c can be denoted as buffer solution because it contains NaF and HF.

Step-by-step solution

Mixtures would result in a buffered solution when 1.0 L of each of the two solutions is mixed

The conjugate base for HF is NaF. The weak acid is HF. The formation of products after the reaction is $\mathbf{0}\mathbf{.}\mathbf{2}\mathit{M}\mathit{H}\mathit{N}{\mathit{O}}_{\mathbf{3}}\mathbf{}\mathit{a}\mathit{n}\mathit{d}\mathbf{}\mathbf{0}\mathbf{.}\mathbf{4}\mathit{M}\mathit{N}\mathit{a}\mathit{F}\mathbf{,}\mathit{N}\mathit{a}\mathit{N}{\mathit{O}}_{\mathbf{3}}\mathbf{\&}\mathbf{}\mathit{H}\mathit{F}$The concentration of NaF has left as the excess which is greater than HNO3.

$\mathit{H}\mathit{N}{\mathit{O}}_{\mathbf{3}}\mathbf{+}\mathit{N}\mathit{A}\mathit{F}\mathbf{\to }\mathit{N}\mathit{a}\mathit{N}{\mathit{O}}_{\mathbf{3}}\mathbf{+}\mathit{H}\mathit{F}$

Thus, the correct option is c.

Reason for incorrect option

Option a. The conjugate base of HNO3is NaNO3. The mixture is a conjugate base and strong acid solution. This is not a buffer solution so incorrect.

Option b. The conjugate base of HF is NaF. The weak acid is HF. The weak and strong acid mixture cannot be taken as a buffer solution. This is incorrect.

Option d. The strong base and acid are NaOH and HNO3. The mixture of strong acid and base cannot be considered a buffer solution and it is incorrect.