Acid Base Equilibrium

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

Use the K_a values to determine whether there are more products or reactants at equilibrium for the given reaction.
K_a NH₄⁺¹= 5.6x10^-10
K_a HCO₃^-1= 4.8x10^-11

• More  products. 
  K_a NH₄⁺¹ > K_a HCO₃^-1
• More  products. 
  K_a NH₄⁺¹ < K_a HCO₃^-1
• More  reactants. 
  K_a NH₄⁺¹ > K_a HCO₃^-1
• More  reactants. 
  K_a NH₄⁺¹ < K_a HCO₃^-1

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

A weak acid, HF, is in solution with dissolved sodium fluoride, NaF. If HCl is added, which ion will react with the extra hydrogen ions from the HCl to keep the pH from changing?

• OH^-
• Na⁺
• F^-
• Na^-

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