pH and Buffers- Lecture 1

Question 1

How would you calculate pH?

Answer 1

pH = - log [H+]

Question 2

_____ donate protons and cause a _____ in pH.

Answer 2

acids

decrease

Question 3

_____ accept protons and cause an _____ in pH.

Answer 3

bases

increase

Question 4

What makes good buffers?

Answer 4

weak acids and weak bases because they only partially dissociate into charged species

Question 5

What do buffers do?

Answer 5

dampen pH changes by providing a reservoir of acid that consumes added base and a reservoir of base that consumes added acid

Question 6

What is the Henderson-Hasselbalch equation for a weak acid?

Answer 6

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

Question 7

What is the Henderson- Hasselbalch equation for a weak base?

Answer 7

pH = pKa + log( [B] / [BH+] )

Question 8

What is the general form of the Henderson- Hasselbalch equation?

Answer 8

pH = pKa + log ( [conjugate base] / [conjugate acid] )

Question 9

The maximum buffering capacity of a weak acid occurs at ______.

Answer 9

one pH unit above of below the pKa.

Question 10

When an acid is in a pH above its pKa, it is ______.

Answer 10

unprotonated and charged

Question 11

When a base is in a pH above its pKa it is _______.

Answer 11

unprotonated and neutral

Question 12

A drug is an acid if its pKa is _____.

Answer 12

less than 7

Question 13

A drug is a base if its pKa is ______.

Answer 13

greater than 7

Question 14

What is the Henderson-Hasselbach equation for the full Bicarbonate buffering system?

Answer 14

pH = 6.1 + log ( [HCO3-] / 0.03 [PaCO2] )

Where 6.1 is the pKa that combines K1 and K2

Question 15

What equation predicts the effect of pH on drug absorption?

Answer 15

[A-] / [HA] = 10^ (pH-pKa)

Question 16

What is the ioselectric point and how can it be calculated?

Answer 16

the pH at which its net charge is zero
pI = (pK1 + pK2) / 2
where pK1 and pK2 border the uncharged state of the molecule