buffers

write the equations to calculate the pH for weak acids and bases

pH = pKa - logC / 2  

pOH = pKb - logC / 2 

how can you calculate pH of a strong acid / base knowing normality

pH = -log10CN

pOH = log10CN 

what is another way you could calculate CN

CN = molarity (moles of acid / base) x valency (number of ionizable H+s/ OH-s per formula unit) 

what is the equation for degrees of dissociation 

and the equations to calculate the dissociated fraction of molecules ([H+] and [A-]) and undissociated fraction of acid molecules 

a = [H+] / c 

undissociated acid fraction = C x (1-a) 

dissociated acid fraction = C x a for both [H+] and [A-] 

knowing the degree of dissociation, how can we calculate Ka?

Ka = a² x c / (1-a)

how can we force weak acids to dissociate more (amount not speed)?

by increasing dilution as increasing the number of H2O molecules → equilibrium shifts to the right to counter the change → HA dissociates more

how do we keep a pH constant?

use a buffer

what is the definition of a buffer 

a mixture of a weak acid and its conjugate base or a mixture of a weak base and its conjugate acid. 

• and the salt / acid ratio should be between 0.1 - 10 

why isn’t a weak acid alone not enough to act as a buffer 

a weak acid on its own dissociates partly, so there isn’t enough A- to react with H+ if a strong acid is added → pH decreases sharply 

and since it’s a weak acid it doesn’t give up its proton too easily which means there isn’t a lot of H+ ions to react with the added OH- ions when a strong base is added → pH increases sharply. 

why does adding a strong base like NaOH create a buffer?

• weak acids dissociate very little → so not enough A- → not a buffer

• strong bases dissociate completely → OH- ions react with H3O+ ions to form 2H2O → removes H3O+ from solution → equilibrium shifts to the right to counteract this change → more acid dissociates

• → Na+ ions react with A- ions → salt formed NaA

• → now solution contains both HA and A- in significant in the right ratio

equation to calculate pH from a buffer solution

pH = pKa + log10[A-]/[HA]

equation to calculate pOH from a buffer solution

pOH = pKb + log10[salt]/[base]

what is the normal pH of the plasma 

physiological pH = 7.4 

what is the pH of the arterial blood and the vein’s?

arterial blood is >7.4

vein blood is <7.4

what is the pH of the cell cytoplasm

7.4

the pH of the blood shifting above or below a certain value will lead to death, what are these values

6.8, and 8.0

what do the terms acidosis and alkalosis mean 

acidosis; when the pH of the blood shifts in the acidic direction below 7.38 

alkalosis ; when the pH of the blood shifts in the basic direction above 7.42 

The pH of the blood’s stability can be compromised, how? name two origins

metabolic origin; pH can increase/decrease due to metabolic factors such as metabolic processes like producing latic acid after hard excercise → acidosis or external sources like consuming certain foods, toxins or meds which can increase / decrease pH → acidosis / alkalosis

respiratory origin; changes in respiratory function e.g. breathing too quickly → alkalosis breathing too slowly → acidosis

what’s the modified henderson-hasselbach equation to calculate the pH of the buffer system of carbonic acid and bicarbonate

pH = 6.1 + log [HCO3-] / 0.03 * pCO2

with 0.03 being CO2 solubility

what is pk in the context of pk1,pk2,

the general dissociation constant and can be used for acids or bases

the number refers to the proton number and the pH associated w it is the pH at which the proton leaves at 

what is the henderson-hasselbach equation to calculate the pH of the intracellularly 

pH = 7.2 + log [HPO4 2-] / [H2PO4-] 

amino acids of proteins also act as buffers, which parts of the proteins act as buffers?

• COOH acts as a weak acid → dissociates a proton to decrease the pH

• NH3+ acts as a weak base → accepts H+ to increase the pH