L2. Significance of pH Flashcards
What is the definition of phosphate?
An inorganic buffer
What is the definition of bicarbonate?
A major buffer in the body
Give the equation to calculate pH.
pH= -log 10 [H+]
What is an acid?
Hydrogen ion donor
What is a base?
Proton acceptor
Give the equation for the dissociation constant.
Ka = [H+][B-] / [A]
acid/conjugate base
Which strength of acid is more easily dissociated?
Stronger acids
What does a large Ka value say about the acid?
Strong acid (as lots has dissociated)
What does a small Ka value say about the acid?
Weak acid (as little has dissociated)
Give the equation to calculate pKa.
pKa= -log 10 Ka
pH= -log 10 [H+] same as this equation but pH = Ka
Give the relationship between Ka and pKa.
They are indirectly proportional due to -log10.
What type of indicators are coloured? Give an example.
Ionised eg In-
What type of indicators are colourless? Give an example.
Unionised eg HIn
How are buffers made?
Using either a weak acid and its conjugate base
or
weak base and its conjugate acid
Where in the body are histatins found?
Saliva
What do histatins contain?
Histidine
When is buffering at its optimum?
[A] = [B-] in the equation [A]= H+ + [B-]
when pKa = pH
solution is half dissociated
