AP Chemistry Unit 8.4: Acid-Base Mixtures

Practice AP Chemistry Unit 8.4 questions on classifying mixed acid-base solutions and representing proton-transfer and buffer formation.

Exam points

Use molecular structure and bonding models to explain polarity, solubility, phase behavior, and properties.
Interpret structural and particle evidence to connect geometry and bonding with observable behavior.

Covered syllabus points

8.4.A—Explain the relationship among the concentrations of major species in a mixture of weak and strong acids and…

[Maximum number: 1]

Methanoic acid, HCOOH, ionizes according to the equation above.

In aqueous solution, the compound $\mathrm{H}_{2} \mathrm{NNH}_{2}$ reacts according to the equation above. A 50.0 mL sample of $0.25 M \mathrm{H}_{2} \mathrm{NNH}_{2}(a q)$ is combined with a 50.0 mL sample of 0.25 M HCOOH(a q).

Is the resulting solution acidic, basic, or neutral? Justify your answer.

When a catalyst is added to a solution of HCOOH(a q), the reaction represented by the following equation occurs.

\mathrm{HCOOH}(a q) \rightarrow \mathrm{H}_{2}(g)+\mathrm{CO}_{2}(g)

For the correct answer and a valid justification: 1 point Acidic. The $\mathrm{K}_{a}$ of $\mathrm{H}_{2} \mathrm{NNH}_{3}{ }^{+}$ is greater than the $\mathrm{K}_{b}$ of $\mathrm{HCOO}^{-}$ , so the production of $\mathrm{H}_{3} \mathrm{O}^{+}$ (aq) occurs to a greater extent than the production of OH (aq). Total for part (d) 2 points

All question bank results loaded

Covered syllabus points

8.4 Acid-Base Reactions and Buffers question 1