Acid-Base Equilibria

When the chemical reaction A + B ↔ C+ D is at equilibrium,

• both the forward and reverse reactions have stopped.
• the sum of the concentrations of A and B equals the sum of the concentrations of C and D.
• all four concentrations are equal.
• neither the forward nor the reverse reactions have stopped.

A substance that ionizes completely in solution is

• an insulator.
• a strong electrolyte. 
• a weak acid.
• a non-electrolyte.

Which is the weakest acid?

• HF
• HNO₂
• CH₃COOH
• HClO

Consider the general equation for an acid in water:
HA(aq) + H₂O ↔ H₃O⁺ + A^-
If there is a lot of product, what does that tell you about the acid?

• K_a > 1  Strong acid
• K_a > 1  Weak acid
• K_a < 1  Strong acid
• K_a < 1  Weak acid

Which of the following is a conjugate acid/base pair?

• HCl/OCl^-
• H₂SO₄/SO₄^2-
• NH₄⁺/NH₃
• H₃O⁺/OH^-

The pH of a solution at 25^ₒC in which [OH-] = 3.9 x 10^-5M is:

• 4.41
• 3.90
• 9.59
• 4.80

Calculate the pH of a 0.47M NH₃ (K_b = 1.8 x 10^-5) solution.

• 2.54
• 8.93
• 5.07
• 11.46

Calculate the [H⁺] in a solution that has a pH of 2.73.

• 5.4 x 10^-12 M
• 1.9 x 10^-3 M
• 2.7 M
• 11.3 M

The pH at the equivalence point of the titration of a strong acid with a strong base is:

• 3.9
• 4.5
• 7.0
• 8.2

Which of the following is not a strong acid?

• nitric
• sulfuric
• perchloric
• hydrofluoric