Lecture 3 - Acids and Bases

Question 1

What is the ion product constant of water at 25?

Answer 1

Kw=10^-14=[OH-][H+]

it is small because water has a very small tendency to dissociate

Question 2

What is the difference between a strong and a weak acid?

Answer 2

strong acids dissociate almost completely, weak acids hold onto their proton tighter, so dissociate to a minimal amount

Question 3

What is the Henderson Hasslebalch equation

Answer 3

pH=pKa+log([A-]/[HA])

Question 4

What is special about the midpoint of a titration curve?

Answer 4

At the midpoint of a titration, the [HA]=[A-] so log of 1=0, so therefore the pKa of an acid is equivalent to the pH at the midpoint of the titration

Question 5

Where is a buffer most useful?

Answer 5

Buffer is most useful when it is in an environment where the pH=pKa because then it can neutralize the maximal amount of both acid and base added, and its buffering powers are highest right in the middle of the buffering range