Acid-Base Equilibria Flashcards
3 AUTHORS who defined Acids and Bases
- Arrhenius
- Bronsted-Lowry
- Lewis
DEFINITION OF ACIDS AND BASES
What did Arrhenius say?
Acid = [H+] in solution
Base = [OH-] in solution
DEFINITION OF ACIDS AND BASES
What did Bronsted-Lowry say?
Acid = (H+) donor
Base = (H+) acceptor
DEFINITION OF ACIDS AND BASES
What did Lewis say?
Acid = e- pair acceptor
Base = e-pair donor
2 properties of Water
Amphoteric = can be an acid or a base
Amphiprotic = can accept o donate a proton
Equation Reaction for Water
2H2O (l) -> <- H3O+ (aq) + OH- (aq)
What is the ION-PRODUCT CONSTANT and its value for water
Kw
Kw of water = 1.0 x 10^-14 at 25 C
4 formulas based on ion-product constant
- pH = -log [H3O+]
- pOH = -log [OH-]
- pKw = -log Kw
- pKw = pH + pOH = 14.00
Do K eq values have a unit? If so, what is it?
No
Shortcut in identifying shift of rxn based on acids and bases
If H3O + is a product, find and compare the reactant and product base. Weaker base -> dito ung shift
If OH- is a product, find and compare the reactant and product acid. Weaker acid -> dito ung shift
SHIFT IN ACID-BASE RXNS
HCl + H2O -> H3O+ + Cl-
H3O+ so compare the bases
RB: H2O
PB: Cl-
HCl is a strong acid so its conjugate base (Cl-) is a very weak base. Thus, the reaction shift is forward, and the formation of H3O+ is favoured
SHIFT IN ACID-BASE RXNS
CH3COOH + H2O -> <- H3O+ + CH3COO-
H3O+ so compare the bases
RB: H2O
PB: CH3COO-
CH3COOH is not a strong acid so its conjugate base (Cl-) is stronger base compared to water. Thus, the reaction shift is reverse, and the formation of CH3COOH is favoured
Relationship between Acids and Bases
The stronger the Acid, the weaker the Base
Kaya… every conjugate base of a strong acid is weaker than water
every conjugate acid of a strong base is weaker than water
Strong Acids Examples (8)
HCl
HBr
HI
HNO3
H2SO4
HClO3
HClO4
Sulfonic Acids
Strong Bases Examples (9)
Commonly Group 1 & 2 + OH
LiOH
NaOH
KOH
RbOH
CsOH
Ca(OH)2
Sr(OH)2
Ba(OH)2
ammonium hydroxides
What is the MOST important rule before doing anything?
BALANCE THE EQUATION
REVIEW!!!
Name the Weak ACIDS/BASES and their conjugates
1.) H2O -> H3O+
2.) H2O -> OH-
1.) Weak Base: H2O ; Conjugate Acid: H3O+
2.) Weak Acid: H2O ; Conjugate Base : OH-
SF rules in Logarithmics
The # of SF in argument will become the # of decimal points in final answer
What will be the equation of Ca(OH)2 (aq)?
Ca(OH)2 is a strong base so one arrow will be used
+ will dissolve into ions
Ca(OH)2 -> (w/ H2O) -> Ca2+ + 2OH-
What will be the equation of HCl (aq)?
HCl is a strong acid so one arrow will be used
+since acid, H2O (l) will be in reactants side to form H3O+
HCl + H2O (l) -> H3O+ + Cl -
Formula for Kw using Ka and Kb
Kw = (Ka)(Kb)
Relationship of
Ka & strength of acid
Kb & strength of base
both direct relationship
What should be shown in solution when there is a need to solve for x using quadrating equation?
SHOW:
Ax^2 + Bx + C = 0
If pH or pOH is given and we want to fine the value of H3O+ or OH -, WHAT to do?
antilog
10^NEGATIVE pH/pOH
Formula for % ionization
% ionization = (amount dissociated) / (initial concentration) x 100
% ionization = (equilibrium concentration) / (initial concentration) x 100
% ionization = (conjugate/weak acid or base not h2o
) x 100
What are buffers?
Solutions that resist drastic pH changes upon addition of small amounts of acids or bases
Criteria for buffers (3)
- Weak acid and salt of its conjugate base
- Weak base and salt of its conjugate acid
- 1 proton difference
How to know if it’s a salt?
No charge since it should form an ionic compound
CH3COOH - NaCH3COO
Equilibrium Rxn
Buffering Action (Acid)
Buffering Action (Base)
Since CH3COOH will donate a proton, it is a weak acid
CH3COOH + H2O (l) -><- CH3COO- + H3O+ (aq)
addition of ACID:
CH3COO- + H3O+ (aq) -> CH3COOH + H2O (l)
addition of BASE:
CH3COOH + OH- (aq) -> CH3COO- + H2O (l)
NH3 - NH4Cl
Equilibrium Rxn
Buffering Action (Acid)
Buffering Action (Base)
Since NH3 will receive a proton, it is a weak base
NH3 + H2O (l) -><- NH4+ + OH- (aq)
addition of ACID:
NH3 + **H3O+ (aq) ** -> NH4 + H2O (l)
addition of BASE:
NH4+ + **OH- (aq) ** -> NH3 + H2O (l)
Are buffering actions complete or partial dissociation?
Complete dissociation
