Topic 4b- Acids and Bases Flashcards
what is the point of a buffer
to maintain the pH when an acid or base is added
adding an acid ion into a solution will
increase the pH therefore will shift the opposite way to keep pH level
strong acid vs a weak acid
strong acid- fully dissociate
weak acid- partially dissociate
ka formula
prod/reac
can we ignore the x again with the 400 rule
yes
after solving x in ice table, what might you have to do
add the x to the original H3O concentration
what are buffers made of
solutions of a weak conjugate acid-base pair
weak acid and its conjugate base
eg HF (WA) / NaF- (F is CB)
resistant to pH changes, even when strong acid or base is added
for our buffer equations what is the A- and what is the HA
A- is base
HA is acid
with buffer equations , when the ratio is 1:1 and they have the same amount of mols what happens
you can cross out the base/acid and your left with pH= pKa
if your acid is more then the conj base then
if your conj base is greater then the acid then
the pka is greater then pH
your pH will be greater then pKa
when do we need to use before and after tables
with STRONG acids and bases added to a buffer
-NOT TITRATION (these would be ice tables)
-weak ones we can just use the HH equation
if were only given mols and no vol, what can we do when plugging it into HH equation
the mols will cancel out, we dont have volume so we dont need to find M
when we have two different volumes what do we need to do
add them together
what happens when strong acids or bases are added to a buffer
all strong acids or bases are consumed
how to determine pH range
-range of pH where buffer system works
-need to choose an acid with a pKa closr to desired pH
- or - of one pH unit
-the buffering capacity is proportional to the concentration or the conjugate acid/base in a solution
steps of adding a strong A or B to a buffer
- determine the neutralization and how its affects solution
- use HH equation to determine pH
-addition of acid ( dissolve completely) A- + HA= HA
-addition of base: HA + OH = A+ + H2O
when writing on our formulas with a strong acid or base being added, what can we leave out
you can take out the ion (Na) from all formulas. eg Na NaC2H3O2 and NaOH
if base= OH- + CH3COOH= H2O + CH3COO-
if 0.020 of a strong acid is added into a buffer solution and its fully consumed, what will happen to the WA and CB before and after the reaction
before: given mols
After: subtract or add the 0.020 mols depending on the side from the before and OH will be 0
titrations will add either a
base to an acid or an acid to a base
pH meter indicates
determines when a solution has reached equivalence point , when the stoich of A equal base
titration of strong acids with strong base will equal
pH 7
-H+ + OH- = H2O
-the pH slowly goes up at the start
-before and after the the equiv point, the pH increases rapidly
-at equiv point, moles acid= moles base and the solution contains only water and salt from the base and acid
-as more base is added, the pH levels off
-base will start higher and go down with the same steps
when working with a titration question that doesn’t say diluted, what cant we do
is C1V1
titrant means
-what is going in the titration
-the other will have a volume with the M if we asked to find volume of the titrant
titration of weak acid with strong base
- OH- + HA -> A - + H2O
-the CB of WA affects the pH when it is formed :
-initial pH of WA is the start
-before equivalence point is the buffer range of pH increasing
-equivalence point is weak CB (wont be 7.0 as it increases)
-after equiv point the OH in excess and level off