Solution Equilibrium & Buffers

Basic buffer is made up of

• weak base and weak acid
• weak base and its conjugate salt
• weak base and its conjugate acid
• strong base and its conjugate acid

Two beakers have liquids in them. When you add a base such as ammonia to beaker 1, the pH did not change. But when you add ammonia to beaker 2, the pH changes drastically. Choose the best explanation.

• Beaker 1 had only water and Beaker 2 contained a buffer.

• Beaker 1 contained a buffer and Beaker 2 contained only water.

• Beaker 2 contained an acid.

• The beaker that changed pH contained a buffer.

Mixtures that would be considered buffers include which of the following?

I. 0.10 M HCl + 0.10 M NaCl

II. 0.10 M HF + 0.10 M NaF

III. 0.10 M HNO₃ + 0.10 M NaNO₃

• I only

• II only

• III only

• II and III

Mixtures that would be considered buffers include which of the following?

• 0.10 M HCl + 0.10 M NaCl

• 0.10 M HF + 0.10 M NaF

• 0.10 M HBr + 0.10 M NaBr

• 0.10 M HI + 0.10 M NaI

The addition of hydrofluoric acid and __________ to water produces a buffer solution.

• HCl

• NaNO₃

• NaF

• NaCl

Which of the following reactions shows what happens when potassium hydroxide is added to an ammonium ion/ammonia buffer?

• OH^- + NH₃ ⇌ NH₃OH

• K⁺ + NH₃⇌ KNH₃

• K⁺ + NH₄⁺ ⇌ NH₄K

• OH^- + NH₄⁺ ⇌ NH₃ + H₂O

A buffer has a pH of 4.85 and contains formic acid and potassium formate.  What can you conclude about the concentrations of the components of the buffer?  The K_a of formic acid is 1.8 x 10^-4.

• Formic acid > Potassium formate
• Formic acid < Potassium formate
• Formic acid = Potassium formate
  
• More information is needed to determine the relative concentrations

What is the pH of a buffer that is 0.080 M NaA and 0.10 HA? (The Ka of HA = 1.0 x 10^-4)

• 2.16

• 3.90

• 4.00

• 4.10

HSO₄¯ + H₂O ↔ H₃O⁺ + SO₄ ^2¯ In the equilibrium represented above, the species that act as bases include which of the following?

• HSO₄^-

• H₂O

• SO₄ ^2¯

• H₂O and SO₄ ^2¯

What is the pH of a solution containing 0.020 M HA and 0.010 A^-? pKa of HA = 5.0.

• 4.70

• 5.30

• 9.30

• 8.70