L2. Significance of pH

Question 1

What is the definition of phosphate?

Answer 1

An inorganic buffer

Question 2

What is the definition of bicarbonate?

Answer 2

A major buffer in the body

Question 3

Give the equation to calculate pH.

Answer 3

pH= -log 10 [H+]

Question 4

What is an acid?

Answer 4

Hydrogen ion donor

Question 5

What is a base?

Answer 5

Proton acceptor

Question 6

Give the equation for the dissociation constant.

Answer 6

Ka = [H+][B-] / [A]

acid/conjugate base

Question 7

Which strength of acid is more easily dissociated?

Answer 7

Stronger acids

Question 8

What does a large Ka value say about the acid?

Answer 8

Strong acid (as lots has dissociated)

Question 9

What does a small Ka value say about the acid?

Answer 9

Weak acid (as little has dissociated)

Question 10

Give the equation to calculate pKa.

Answer 10

pKa= -log 10 Ka

pH= -log 10 [H+] same as this equation but pH = Ka

Question 11

Give the relationship between Ka and pKa.

Answer 11

They are indirectly proportional due to -log10.

Question 12

What type of indicators are coloured? Give an example.

Answer 12

Ionised eg In-

Question 13

What type of indicators are colourless? Give an example.

Answer 13

Unionised eg HIn

Question 14

How are buffers made?

Answer 14

Using either a weak acid and its conjugate base
or
weak base and its conjugate acid

Question 15

Where in the body are histatins found?

Answer 15

Saliva

Question 16

What do histatins contain?

Answer 16

Histidine

Question 17

When is buffering at its optimum?

Answer 17

[A] = [B-] in the equation [A]= H+ + [B-]
when pKa = pH
solution is half dissociated