Acid-Base Equilibrium Flashcards
Acids
Proton donor, must have an H+ to give up
Bases
Proton acceptor, must have a lone pair of e- that can form a coordinate covalent bond (CCB) with H+ OR a negative charge to attract an H+ (F-)
Acid Base Reaction
Involves transfer of H+ from acid to base (Competition for a p+ between two bases)
Salt
Substance that can produce an acidic or basic solution
Amphoteric Substance and Hydrolysis of Amphoteric Ions
A substance that can act as a B-L acid or base. Has an H+ to donate and a -charge / lone pair to accept a proton
All polyatomic ions whose chemical formula begins with H are amphoteric (HC3-), these can either donate or receive a proton when dissolved in water.
Conjugate Acid-Base Pair
Two substances whose chemical formula differs by only one H+
[H3O+] and pH
pH = -log[H3O+] or [H3O+] = 10^-pH
[OH-] and pOH
pOH = -log [OH-] or [OH-] = 10^-pOH
Eq law for the rxn of H2O undergoing autoionization
K(w) = [H3O+] [OH-]
[H3O+] vs [OH-]
Acid Solutions: Dissolving acids in H2O : [H3O+] >1.0x10^-7M, [H3O+] >[OH-]
Basic Solutions: Dissolving bases in H2O : [OH-] >1.0x10^-7M, [H3O+] < [OH-]
Neutral : =
Percent Ionization
Indicates the extent to which an acid will ionize in water (SA have 100 percent)
p = ( [ionized acid] / original [acid solute] )x 100
p = ( [H3O+] / [weak acid] )x 100
Ionization Constants
Weak Acid Ionization constant Ka = [H3O+] [acid ion] / [HA]
Weak Bases Ionization constant Kb = [OH-] [HB] / [base ion]
Polyprotic Acids
Possess more than one ionizable proton (H+), donate in steps, Ka decreases per step so that K1>K2>K3…
Hydrolysis
The reaction of an ion with water to produce an acidic or basic solution, ion exchanges a H+ with a water molecule in a B-L acid-base rxn
Salts that form Neutral Solutions
Salt contains cation of a strong base (group 1/2) AND anions of strong monoprotic acids (Cl-, Br-, I-, NO3-)
They do not exchange an H+ with water and thus have no effect on pH of solution
Salts that form Acidic Solutions
Salt contains cations that are weak acids
Salts that form Basic Solutions
Salt contains anions that are weak bases
Salts that act as Acid and Base
Salts contain a weak base and a weak acid, may form an acidic/basic solution.
Strong vs Weak Acids
SAs completely ionize in H2O, produce high [H3O+], great electrolytes, undergo rapid rxns
WAs partially ionize in water b/c of strong attraction for their H+, creates an easy system that lies far to the left, poor electrolytes, undergo slow rxns
Strong Bases vs Weak Bases
SBs completely dissociate in H2O, produce metal cations and OH- ions, great electrolytes, undergo rapid rxns
WBs don’t ionize completely in H2O, are B-L base that have poor attraction for H+, usually non-metal/polyatomic anion that reacts w/H2O to form eq that includes OH- : B- + H2O HB + OH-, poor electrolytes
Buffers
Resists large changes in pH when moderate amount of acid/base is added by shifting in the direction that opposes the stress acc to LeChat’s Principle.
Buffer Capacity
Buffer Capacity is the limit to the amount of SA/SB that can be neutr. by buffer before pH begins to rise rapidly. Is determined by the [ ] of the conjugate A-B pair. Eq for determining pH of Buffer: [H3O+] = x = ka( [HA]/[A-] ); [OH-] = x = kb( [HB]/[B-] )
SA-SB Titration Calculation
@beginning : 100 percent ionzes, pH = -log[H3O+]
*b/c H+ = H3O+
After add: NIE, ICE, pH = -log( )
@eq : pH = 7
WA-SB Titration Calculation
@beginning : x = [H3O+] = sqrt. Ka[HA]
After add : x = [””] = Ka( [HA]/[A-] ) assumptions
@eq : x = [OH-] = sqrt. Kb[B-]
Beyond : HA + OH- -> H2O + A-, ICE, pOH = -log, pH = 14-pOH
