AP Chemistry Buffers

Buffer is defined as

• ability to resist pH change
• ability to prevent pH from decreasing
• ability to resist a pH increase
• ability to resist pH change when small amount of acid added

Acidic buffer is made up of

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

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

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

Which pair is the most effective buffer?
Ka of HIO is 1.7 x 10^-11
Ka of HF is 3.5 x 10^-4

• 0.5 M HIO and 0.5 M NaIO
• 0.1 M HF and 0.1 M NaF
• 0.9 M HIO and 0.1 M NaIO
• 0.1 M HF and 0.7 M NaF

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 0.08 M NaA and 0.1 HA. The Ka of HA = 1.0 x 10^-4.

• 2.16
• 3.91
• 4.00
• 4.10