Question

A 1.0-L buffer solution is 0.130 M in HNO2 and 0.195 M in NaNO2.

-Determine the concentrations of HNO2 and NaNO2 after addition of 1.2 g HCl.
-Determine the concentrations of HNO2 and NaNO2 after addition of 1.2 g NaOH.

Answer 1

After adding 1.2 g HCl, the concentrations are approximately 0.130 M HNO₂ and 0.195 M NaNO₂. After adding 1.2 g NaOH, the concentrations remain approximately 0.130 M HNO₂ and 0.195 M NaNO₂ due to the buffer's capacity to resist significant changes in pH.

Step-by-step explanation:

When HCl is added, it reacts with NaNO₂ in the buffer to form NaCl and HNO₂. The balanced equation for this reaction is:

`\[HCl + NaNO_2 \rightarrow NaCl + HNO_2.\]`

Since the reaction consumes HNO₂, the concentration of HNO₂ decreases slightly. The new concentration of HNO₂ is calculated using the stoichiometry of the reaction and the given quantities. Conversely, the concentration of NaNO₂ increases due to the formation of NaCl. The final concentrations are determined by adjusting the initial concentrations with the changes caused by the reaction.

When NaOH is added, it reacts with HNO₂ in the buffer to form NaNO₂ and H₂O. The balanced equation for this reaction is:

`\[NaOH + HNO_2 \rightarrow NaNO_2 + H_2O.\]`

Since the reaction consumes HNO₂, the concentration of HNO₂ decreases slightly. The new concentration of HNO₂ is calculated using the stoichiometry of the reaction and the given quantities. Conversely, the concentration of NaNO₂ increases due to the formation of NaNO₂. The final concentrations are determined by adjusting the initial concentrations with the changes caused by the reaction. Overall, these calculations are based on the principles of stoichiometry and the conservation of mass in chemical reactions.