AP Chem Unit 08 Multiple Choice Mock Exam

CH₃CH₂COOH(aq) + H₂O(l) ⇄ CH₃CH₂COO^─(aq) + H₃O⁺(aq)

 

Propanoic acid, CH₃CH₂COOH, is a carboxylic acid that reacts with water according to the equation above. Identify a Brønsted-Lowry conjugate acid-base pair in the reaction. Clearly label which is the acid and which is the base.

• Acid: CH₃CH₂COOH

  Base: CH₃CH₂COO^─

• Acid: CH₃CH₂COOH

  Base: H₃O⁺

• Acid: H₂O

  Base: H₃O⁺

• Acid: H₂O

  Base: CH₃CH₂COO^─

Which of the following substances is amphoteric (could act as both a Brønsted-Lowry acid and base)?

• H₃O⁺

• H₂SO₄

• HSO₄^─

• SO₄^2─

HF(aq) + H₂O(l) ⇄ H₃O⁺(aq) + F⁻(aq)

The equilibrium constant, K_a, for the reaction above is 7.2x10^-4.  Which answer shows the bases and their relative strengths?

• F⁻ > H₂O

• HF > H₃O⁺

• H₂O > F⁻

• H₃O⁺ > HF

Which of the following images best represents a solution of sulfuric acid, H₂SO₄, in water?

• (a)

• (b)

• (c)

• Either (a), (b), or (c) depending on the temperature of the acid solution.

What is the percent ionization at 25˚C for a weak acid, HA, that is 0.40 M? K_a = 4.0×10⁻⁷ for this acid at 25˚C.

• 0.050%

• 0.20%

• 2.0%

• 0.10%

Equal moles of the indicated acids are dissolved in the amounts of water shown in the beakers above.  In which solution will the percent ionization be the lowest?

• Beaker 1

• Beaker 2

• Beaker 3

• Beaker 4

Tags

NGSS.HS-PS1-5

The auto-ionization of water is an endothermic process.  Use LeChatelier's Principle to predict the value of the pH of water as the temperature of water is decreased from 25°C to 10°C.

• pH DECREASES; Cooler temperatures shift the equilibrium to the RIGHT.

  LARGER [H₃O⁺] ∴ LOWER pH

• pH INCREASES; Cooler temperatures shift the equilibrium to the RIGHT.

  LARGER [H₃O⁺] ∴ HIGHER pH

• pH INCREASES; Cooler temperatures shift the equilibrium to the LEFT.

  SMALLER [H₃O⁺] ∴ HIGHER pH

• pH DECREASES; Cooler temperatures shift the equilibrium to the LEFT.

  SMALLER [H₃O⁺] ∴ LOWER pH

Tags

NGSS.HS-PS1-5

The pH of 0.1 M HBrO (hypobromous acid) aqueous solution was measured to be 5.0. What is the approximate value of the K_a and pK_a for hypobromous acid?

• K_a = 1x10^-9 and pK_a = 9

• K_a = 1x10^-11 and pK_a = 11

• K_a = 1x10^-5 and pK_a = 5

• K_a = 1x10^-3 and pK_a = 3

HC₂H₃O₂(aq) + H₂O(l) ⇌ H₃O⁺(aq) + C₂H₃O₂^–(aq)

HC₂H₃O₂(aq), a weak acid (K_a = 1 x 10^–5), dissociates in water according to the equation above. Which of the following provides the best estimate of the pH of 0.1M HC₂H₃O₂(aq) and identifies the species at the highest concentration (excluding H₂O) in the solution?

• pH = 3

  Species at Highest Concentration = HC₂H₃O₂(aq)

• pH = 1

  Species at Highest Concentration = HC₂H₃O₂(aq)

• pH = 3

  Species at Highest Concentration = C₂H₃O₂^–(aq)

• pH = 1

  Species at Highest Concentration = C₂H₃O₂^–(aq)

The pH of a solution prepared by the addition of 200.mL of 0.004M NaOH(aq) to 600.mL of distilled water is closed to

• 3

• 4

• 10

• 11