A solution of a compound is treated with indicators and gives the following results. What is the approximate pH range of the solution? (Use the table provided to you in your lab manual.)

Methyl violet - violet
Thymol blue - yellow
Methyl yellow - yellow
Bromcresol green - green

• 1 to 2
• 6 to 7
• 4 to 5

4 to 5

You are going to be asked to prepare a buffer from a weak acid and its conjugate base. What volume of each component will be used?

• 25.0 mL
• 15.0 mL
• 20.0 mL
• 10.0 mL

15.0 mL

A buffer is made up of equal volumes of 0.1 M weak acid (AH) and 0.1 M conjugate base (A ^minus). The pH of the solution is measured to be 4.6. What is the pK_a of this weak acid?

(HINT: Use the formula pH = pK_a + log(Vol A ^minus/ Vol HA))

• 2.6
• 4.6
• 5.6
• 3.6
• 1.6

4.6

A buffer is made up of 2.0 mL of 0.1 M weak acid (AH) and 20.0 mL of 0.1 M conjugate base (A ^minus). The pH of the solution is measured to be 5.2. What is the pK_a of this weak acid?
(HINT: Use the formula pH = pK_a + log(Vol A ^minus/ Vol HA))

• 6.2
• 5.2
• 2.2
• 3.2
• 4.2

4.2