BUFFERS

A buffer solution is prepared by mixing equal volumes of 0.50 M weak acid with 1.0 M of its conjugate base. Based on the data given in the table above, which of the following pairs of chemical solutions should be used to prepare the buffer solution so that the pH will be between 4 and 7?

• CH₃COOH and NH₃

• CH₃COOH and CH₃COONa

• H₂CO₃ and NH₃

• H₂CO₃ and Na₂CO₃

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

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¯

Which solution A and B of equal volume and concentration mixed together to form a buffer?

• Nitric acid and potassium hydroxide
• Nitric acid and potassium nitrate
• Propanoic acid and potassium hydroxide
• Propanoic acid and potassium propanoate

What is the pH of a solution containing 0.02 M HA and 0.01 M A^-? pKa of HA = 5.0.

• 4.70

• 5.30

• 9.30

• 8.70

Calculate [H3O+] in a solution that is 0.10 M in HF and 0.20 M in NaF. Ka for HF = 6.8x10^-4

• 3.47

• 3.17

• 3.39x10^-4

• 6.76x10^-4

Calculate the pH of a solution consisting of 15g of HF and 21g of NaF in 750 mL solution. Ka for HF = 6.8x10^-4

• 3.31

• 3.03

• 3.41

• 2.97

When making a buffer of pH = 5, acids with the following K_a values are available. Which would be the best acid to use?

• 1.8 x 10^-5

• 1.8 x 10^-8

• 4.9 x 10^-10

• 3.0 x 10^-8

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

Suppose you have a solution of 0.3 M HBrO and 0.3 M BrO. You add a small amount of NaOH to this buffer solution. What is the reaction that takes place?

• H⁺ + BrO^- --> HBrO

• OH^- + H⁺ --> H₂O

• OH^- + HBrO --> H₂O + BrO^-

• OH^- + BrO^- --> O^-2 + HBrO