Acids and Bases Flashcards
Defined an acid as a species that donates H+ (protons) in an aqueous sol’n and a base as a species that produces OH- (hydroxide ions) in an aqueous sol’n
Arrhenius
any species that donates protons
*Do not necessarily have to dissociate into H+ in aqueous sol’n
Bronsted-Lowry acid
any species that accepts protons
*Do not necessarily have to dissociate to form OH- in aqueous sol’n
(Ex: NH3 and Cl-)
Bronsted-Lowry base
Defines a ______ as an electron-pair acceptor
Lewis acid
defines a _____ as an electron-pair donor
lewis base
Bronsted-Lowry acids and bases always occur in pairs, called _______. The two members are related by the transfer of a proton
conjugate acid-base pairs
The stronger the acid, the _______ its conjugate base
weaker
the weaker the acid, the ________ its conjugate base
stronger
H2O can act as either a ________ or a _____ with other species or with itself
H2O + H2) —-> H3O+ + OH-
proton donor or acceptor
Constant that describes _______, or acting as a proton donor/acceptor toward itself
Autoionization: Kw
Equation: Kw (Autoionization constant)
Keq = Kw = [H3O+][OH-]
Note: Kw for water = 110^-14
measures hydrogen ion (proton) concentration
pX = -log(X) where [H+] is its molarity and the logarithm is of base 10
pH
Equation: pH
pH = -log[H+] = log (1/[H+])
The power to which 10 would be raised to obtain the number x
Log(x)
i.e. [H+] = 1 * 10^-3 then pH = 3
have a pH less than 7
relative excess of H+ ions
Ex: Lemon juice, gastric juice
acidic sol’n
pH greater than 7
relative excess of OH- ions
Ex: baking soda, bleach, ammonia
basic sol’n
pH = 7
Ex: water
neutral sol’n
completely dissociate into their component ions in aqueous sol’n
strong acid and bases
Examples of this include: HClO4, HNO3, H2SO4, HCl, HBr, HI
strong acids
Examples of this include: NaOH, KOH, soluble hydroxides of Group IA and IIA metals
strong bases
substances that do not ionize completely (only partially)
weak electrolytes
weak acids and bases
equilibrium constant for acid ionization
acid dissociation constant
measure of the degree to which an acid dissociates
smaller for weaker acids
Ka
equilibrium constant for base ionization
Kb
the smaller the _____, the weaker the acid (i.e. must smaller than 1)
Ka
Equation: Ka
Ka = [H+][A-] / [HA]
Note: [A-] = conjugate base; [HA] = weak acid
Strategy: Calculate the pH for sol’ns of weak acids
- ID start concentration for weak acid (reactant) and H+ and A- (product)
- Calculate change in concentration
- ID end concentration of weak acid (reactant) and H+ and A-
The concentratino of teh weak acid at equilibrium = it’s initial concentration minus the _______
amount dissociated
The concentration of [H+] dissociated from a weak acid equals ______
amount of conjugate base formed
the addition of a sol’n of known concentration and volume to another sol’n to determine its unknown concentrations
involved the addition of a sol’n to determine its concentration
titrations
add base of precisely known concentration drop by drop to an acid solution until the numbero f moles of base added equals the number of moles of acid initially present
acid-base titration
point at which the number of moles of base added equals the number of moles of acid initially present in an acid-base titration
equivalence point
Equation: Acid-Base titration at equilibrium point
Va * Ma = Vb * Mb
Note: Va = initial volume of acid solution; Ma = acid’s molarity (trying to determine); Vb = volume of base added; Mb = molarity of the base (known precisely before)
T/F: The equivalence point in an acid-base titration must occur at pH 7
False
Titrations between a strong acid and strong base have an equivalence point at pH =
7
titration between a weak acid and a strong base has an equivalence point at pH ______
> 7
