TEST 4- 14.7-14.12, 15 Flashcards
Autoionization of water yields
the same number of hydronium and hydroxide ions
Monoprotic
can only accept or donate one proton
Polyprotic
has more than one proton it can donate or accept
Monoprotic example
HCl, NaOH, NaCl, H2O
Polyprotic example
acid H2SO4, base Ca(OH)2
Characteristics of strong acid
large Ka and small PKa
Characteristics of strong base
large kb and small PKb
When a strong acid or strong base produces concentrations of H3O+ and OH- that are greater than
10^-6 contributions from autoionization can be ignored
In autoionization of water, K
Kw is used
An increase difference in pKas
further equilibrium lies toward higher pKa (or weaker acid)
Ka is much larger in which step
first step
For pH of strong acids and bases when must autoionizaiton of water be a factor
when [H3O+] is less than 10^-6
Higher electronegativity Acid
stronger acid, increases across period
Larger atom Acid
stronger acid, increase down group
Higher electronegativity Base
weaker base, increase from right to left
Larger atom Base
weaker base, increase up group
The strength of an acid, HA depends on
strength or stability of its conjugate base A-
More stable conjugate base
stronger conjugate base
More positive charge
stronger acid
F- is the most stable conjugated base
HF is the strongest acid
Weaker base (stable or not)
more stable
CARDIO
Charge, atom (electronegativity and size), resonance (stabilization), dipole induction (nearby electronegativy substituent), orbitals (hybridization)
Charge
more positive is more acidic, more negative more basic
Atom
atom next to acidic hydrogen, if same row look at electronegativity, if same group look at size
Resonance
of conjugate base, more resonance, more stable, stronger
Dipole induction
more electronegative substitute and closer to hydrogen is more acidic
Orbitals
higher s character is more acidic
If two atoms have the same structure
closer to acidic hydrogen is more acidic
S versus P orbitals
s orbitals are closer to the nucleus and are more electronegative, higher % s orbitals is more acidic
4 electron domains
SP3
Conjugate acid of weak base
acidic
Conjugate base of weak acid
basic
Conjugate base from strong acid
neutral
Conjugate acid from strong base
neutral
Cation of strong base
neutral
Weak acid and weak base
if ka > kb it is acidic, if kb > ka it is basic
Amphoteric ion acidity
compare ka with its own kb, the larger one dominates
Bigger ion
weaker bond, stronger acid
Strong acid with strong base
Large equilibrium constant, water and neutral salt as product, neutral effect on solution
Strong acid with weak base
Large equilibrium constant, water and acidic salt as products, acidic effect on solution
Weak acid with strong base
Large equilibrium constant, water and basic salt as products, basic effect on solution
Weak acid with weak base
Small equilibrium constant, water and salt as products whose pH depends on strength of conj acid and base present, effect on solution depends on pH
Example of strong acids that will not effect pH
Cl, Br, I, NO3, ClO4
Examples of strong bases that will not effect pH
Li, Na, K, Mg, Ca, Sr, Ba
Acidic pH < 7
NH4+, HSO4-, HSO3-, H3PO4-
Basic pH > 7
CH3CO2-, HCO2-, HCO3-, F-, CN-, HS-, NO2-, OCl-, CO3 2-, S 2-, SO3 2-, PO4 3-
Neutral pH = 7
Li+, Na+, K+, Mg2+, Ca2+, Sr2+, Ba2+, Cl-, Br-, I-, NO3-, ClO4-
Which are ignored for strong bases
Na+ and K+
Which are ignored for strong acids
Cl- and NO3-
If acidic hydrogen is on the same atom in two compounds
cannot consider electronegativity or size
If acidic hydrogen is on a different atom in two compounds
cannot consider hybridization, resonance, or inductive
What is needed to make a buffer
a weak acid and its conjugate base or a weak base and its conjugate acid
Most effective buffers
pH values within range of + - 1 of the pKa of weak acid
If the ratio of weak acid to conjugate base remains close to original buffer solution
even after acid or base is added, the pH will not be altered drastically
When can you ignore -x
If Ka * 100 < [HA]0
Buffer equation pH=
pH = pKa + log (conjugate base) / (weak acid)
Common Ion Effect
When a reagent added to a solution already in equilibrium (ion already present), the reaction will shift opposite of addition
Shift in common ion effect
opposite of addition
To get rid of log in an equation
10^
To get rid of ln in an equation
e
Adding a strong acid to a buffer
will react with the basic component of the buffer and produce the acidic component of the buffer
Adding a strong base to a buffer
will react with the acidic component of the buffer system and produce the basic component of the buffer
When given additive volume in a problem
convert to mol to use with log
Titration curve
plot of pH versus volume of titrant added to solution
At equivalence point
number of moles of base is equal to number of moles of acid
Half equivalence point
pH = Pka
End point
no further change in pH
Titration of strong acid with strong base
neutral salts, pH at equivalence will always be 7, [H3O+] and [OH-] always is 1*10^-7 M
The compound in excess if strong acid or base
will hydrolize in water in a second step (NaOH -> Na+ + OH-) then find pOH and pH
To neutralize a reaction
moles of H+ = moles of OH-
Titration of weak acid with strong base
basic salt produced, pH greater than 7, at half equivalence [weak acid] = [conjugate base], Ka = [H3O+] and pKa = pH
Titration of weak base with strong acid
acidic salt produced, pH less than 7, pKb = pOH
What in ICE table affects pH
when the lower number is subtracted in “C” to = 0, that value does not affect
pH indicators
allow for a color change to take place when the pH of the solution that the indicator dissolves in reaches some point
Maximum buffer capacity
when [HA] and [A-] are large
Buffer range
pKa + - 1
Weaker acid
stronger conjugate base
Best buffer shows
least change in pH
Finding volume in titration
volume = mol / M
The most what means the greater buffer capacity
greatest HA and A-
If you add strong acid to a solution of weak acid
diminishes the amount of weak acid ionization
The more stable to conjugate base of an acid
the more acidic the acid is
What determines acidity
stability of conjugate base
Meaning of pKa
pKa = pH at which [HA] = [A-]
Acids with multiple ionizable protons will have
multiple Ka’s for each proton and therefore multiple pkas
pH > pKa
proton off
pH < pKa
proton on, more acidic
strong acid and strong base graph
pH = 7
If strong acid is added to a buffer
will react with weak base, slightly decrease pH
If you add a strong acid to a solution of weak acid
diminishes weak acid ionization
If you add strong base to a solution of weak base
diminishes weak base ionization
More stable
more acidic
In a buffer what is the limiting reactant
strong base
Buffer resists change in pH when
acid added, base added, buffer is diluted
Have no effect on pH
neutral salts (NaCl)
Examples of strong electrolytes
salts, strong acids, strong bases
In a reaction with strong electrolytes
one direction reaction with electrolyte on reactant side
