1. Ionization of water, dissociation of weak acids, and buffers Flashcards
What are the two products from the ionization of water?
proton (H+)
hydroxide ion (OH-)
What happens to hydrogen ions as water is ionized?
they hydrate to form hydronium ions
How great of a chance does water have to ionize?
small
What side of this equation does equilibrium lie?
H2O = H+ + OH-
left
What is the Keq of the ionization of water?
low
What happens to protons existing in a free solution?
hydrated to form hydronium ions (H3O+)
Do free H+ ions ever exist in water?
no
Why do protons hop?
hydronium ions are solvated by nearby water molecules, loosing the proton, which will create another hydronium ion and the process continues
What is Kw?
ionic product of water
What does the concentration of [H+] and [OH-] equal in pure water?
1*10^-7 M
What does the pH scale designate?
the [H+] and [OH-] concentrations
What is ‘p’ defined as?
the negative log of ‘something’
What is the formula for pH?
-log[H+]
What happens when you take the negative log of the Kw equation?
pH + pOH =14
Is an acid or base a proton donor?
acid
What does the expression ‘the pH scale is logarithmic’ mean?
change in 1 unit results in a 10 fold change
What is a change in pH really a change of?
proton concentration
Define alkaline
pH greater than 7
Define acidic
pH less than 7
What is the unit for ion concentration when calculating pH?
mols/L
What will strong acids have a lot of?
protons able to be donated
How do WEAK electrolytes interact with water?
only partially dissociate
What does Ka measure?
the extent of acid dissociation
What is a conjugate acid- base pair?
proton donor and its corresponding proton acceptor
What does pKa measure?
acidity
what is the equation of pKa?
-log(Ka)
What is a titration curve?
a plot of pH against the amount of NaOH added
What are buffers?
resist change in pH
At what ratio is there a 50:50 mixture of acid and anion forms of the compounds?
pH = pKa
What is the buffering zone?
1 pH below and above the midpoint
Where is the buffering capacity greatest?
when pH = pKa
What three things does the Henderson - Hasselbalch equation relate?
pH
pKa
buffer concentration
What does the Henderson - Hasselbalch equation describe?
shape of the titration curve of any weak acid
Why do cells use the buffer system?
to maintain intracellular pH levels
What three weak acids are important for in vivo buffer systems?
phosphate
bicarbonate
histidine
What two things does the bicarbonate buffer system depend on?
[HCO3-]
partial pressure of CO2
