Buffer Solutions and pKa Concepts

The video tutorial explains buffer solutions, which consist of a weak acid and its conjugate base, and their ability to resist changes in pH. It introduces the Henderson-Hasselbalch equation to determine the effective pH range of a buffer. The tutorial discusses the conditions under which buffers are most effective, particularly when the concentrations of the weak acid and conjugate base are equal. It also covers how to calculate the effective pH range by considering when one component's concentration is ten times that of the other. Finally, it guides on choosing an appropriate buffer solution based on the desired pH and the pKa of the weak acid.

What is the primary role of a buffer solution?

• To increase the pH of a solution

• To neutralize a solution

• To decrease the pH of a solution

• To resist large changes in pH

In the Henderson-Hasselbalch equation, what does the term 'pKa' represent?

• The concentration of the weak acid

• The concentration of the conjugate base

• The pH of the solution

• The dissociation constant of the weak acid

When is a buffer solution most effective at resisting pH changes?

• When the pH is far from the pKa

• When the concentration of the conjugate base is much higher than the weak acid

• When the concentration of the weak acid is much higher than the conjugate base

• When the concentrations of the weak acid and conjugate base are equal

What happens to the effectiveness of a buffer if one component's concentration is more than 10 times the other?

• The buffer's pH becomes acidic

• The buffer's pH becomes neutral

• The buffer becomes less effective

• The buffer becomes more effective

What is the upper limit of the effective pH range when the conjugate base concentration is 10 times that of the weak acid?

• pKa + 2

• pKa - 1

• pKa

• pKa + 1

What is the lower limit of the effective pH range when the weak acid concentration is 10 times that of the conjugate base?

• pKa

• pKa + 2

• pKa - 1

• pKa + 1

How is the effective pH range of a buffer determined?

• By the volume of the solution

• By the concentration of the buffer components

• By the pKa value of the weak acid

• By the temperature of the solution

Why is an ammonium-ammonia buffer chosen over an acetic acid-acetate buffer for a pH of 9?

• Because it has a higher pKa value

• Because it is more acidic

• Because its effective pH range includes 9

• Because it is cheaper

What is the effective pH range of an ammonium-ammonia buffer with a pKa of 9.25?

• 8.25 to 10.25

• 7.25 to 9.25

• 9.25 to 11.25

• 6.25 to 8.25

What is the pKa value of acetic acid at 25 degrees Celsius?

• 6.74

• 3.74

• 4.74

• 5.74