chem 106 test 3 Flashcards
acid characteristics
H+, low pH, sour, litmus turns red
base characteristics
OH-, high pH, bitter, turn litmus blue
strong acids
HCl, HBr, HI, H2SO4, HNO3
strong bases
alkali metals + hydroxide (e.g., NaOH, KOH)
opposite of strong is
negligible
opposite of weak is
weak
opposite of negligible is
strong
Ka > 1
strong acid
Ka < 1
weak acid
higher Ka means
stronger acid
Kw =
[H3O+][OH-] = 1.0 x 10^-14
significant figures inside the log yields # ? outside of the log
decimal places
(e.g., -log(1.0x10^-12)=12.00
2 SF => 2 decimal places)
Ka =
[H3O+][A-] / [HA]
% ionization
change / initial
you can assume x is negligible if
x < 5% of the initial (Ka really small means x is probably really small)
anions
conjugate bases of some acid (weak acid => weak base, strong acid => negligible base)
cations
if they contain H+’s, they may be acidic
cations from weak bases + CB strong acid will affect pH in this way:
lower (NH4Cl)
cations from strong bases + CB strong acid will affect pH in this way:
no change (NaCl)
cations from weak bases + CB weak acid will affect pH in this way:
? must tell by Ka and Kb (NH4F)
cations from strong bases + CB weak acid will affect pH in this way:
increase (NaF)
polyprotic acids: if Ka1 > Ka2 by 10^3, ?
the second dissociation is negligible
common ion effect
adding a strong acid to a weak acid solution will increase [H+] and shift equilibrium left
buffers
solutions that resist change in pH (weak acid and its conjugate base - e.g., HOAc and OAc-)
How to recalculate [HX] and [X-] after addition of strong acid
strong acid will use up [X-] to form more [HX], so subtract from the base and add to the acid
How to recalculate [HX] and [X-] after addition of strong base
strong base will use up [HX] to form more [X-], so subtract from the acid and add to the base
pH of blood
7.35-7.45
3 factors that shift HbH+ + O2 HbO2 + H+ to the left
- consumption of O2 in muscle
- increase in body temp.
- CO2 and lactic acid generated by metabolism
titrations
known concentration of base is added to an acid of unknown concentration or strength to determine concentration or strength
equivalence point
[acid] = [base]
4 zones to graph titration curve
- initial pH
- before equivalence point
- at equivalence point
- after equivalence point
how to calculate initial pH if acid is in the flask
pH = -log[strong acid]
how to calculate pH before equivalence point if acid is in the flask
pH = -log[(mol acid - mol base) / (volume acid + volume base)]
how to calculate pH at the equivalence point
pH = 7
how to calculate pH after the equivalence point if acid began in the flask
pH = 14 - (-log[(mol base - mol acid) / (volume base + volume acid)])
