buffers

Question 1

what is a buffer solution

Answer 1

system that minimise ph change
when small amounts acid alkali added

Question 2

what two components to buffer solution contain

Answer 2

weak acid HA removes added alkali
conjugate base A- removes added acid

Question 3

prep weak acid and its salt

Answer 3

ch3cooh and ch3coona
ch3cooh > h+ + ch3coo-
ch3coona + aq > ch3coo- + Na

ch3coo- and ch3cooh are the 2 components

Question 4

prep by partial neutralisation of weak acid

Answer 4

add aq solution of alkali like NaOH to excess weak acid
weak acid partially neutralised by acid
forms conjugate base
resulting solution - mix of salt of weak acid and any unreacted weak acid

Question 5

how does conjugate base removed added acid

Answer 5

Ha ⇌ H+ + A-
addition of acid so H+ increases
and they react with conjugate base - A-
so equilibrium shifts left removing most H+
same in blood H2CO3 ⇌ H+ + HCO3-
H+ reacts with HCO3- shifting left

Question 6

how does weak acid remove added alkali

Answer 6

Addition of OH-
small conc of h+ reacts with oh-
H+ + OH- > H20
HA dissociates shifting eqb right to restore most H+ ions
Ha ⇌ H+ + A-

blood
H2CO3 ⇌ H+ + HCO3-
H2C03 dissociates so eqb shifts right to restore most H+