Experiment 2 Flashcards
pH
-log[H+]
-Low pH values correspond to high H3O+ concentrations (acidic)
-High pH values correspond to low H3O+ concentrations (basic)
[H+]
10^-pH
pOH
-log[OH-]
ionization of water
-H2O (l) ⇄ H+ (aq) + OH- (aq)
or
-H2O (l) + H2O (l) ⇄ H3O+ (aq) + OH- (aq)
Kw, equilibrium constant for ionization of water
-Kw = [H3O+][OH-]
-pKw = pOH + pH
-Kw = 1x10^-14
-pKw = 14
-Kw = (Ka)(Kb)
Neutral solution
concentrations of hydronium (H3O+) and hydroxide (OH-) ions equal each other
Acidic solution
solution with pH < 7
Basic solution
solution with pH > 7
Arrhenius acid
substances that increase [H+] in water
Arrhenius base
substances that increase [OH-] in water
Bronsted-Lowry acid
a substance that can donate a proton (H+)
Bronsted-Lowry base
a substance that can accept a proton (H+)
Strong acid
-ionization strongly favors formation of products when acid is reactant
-HCl, HBr, HI, HClO3, HClO4, H2SO4, HNO3
Weak acid
acid that only ionize to small extent
Strong base
-ionization strongly favors formation of products when base is reactant
Weak base
base that only ionizes to small extent
Ionization of acid (HA) equation
HA + H2O ⇄ H3O+ + A-
-HA is acid, A- is conjugate base
Ionization of base (B) equation
B + H2O ⇄ OH- + BH+
-Where B is a base and BH+ is its conjugate acid
Ka (acid ionization constant)
Ka = [H3O+][A-] / [HA]
Kb (base ionization constant)
Kb = [OH-][BH+] / [B]
Salt
-the product of the reaction between an Arrhenius acid and base
-Proton of acid combines with hydroxide ion of base to form water, remaining species from acid and base combine to make salt
-When a salt dissolves in water, it dissociates and releases to the solution its cation as a conjugate acid and its anion as a conjugate base
Amphiprotic solutions
-a substance that can both donate or accept protons
-pH = ½ (pKa1 + pKa2)
Standard solution
a solution whose concentration is accurately known
Standardization
process of determining the accurate concentration of a solution
Primary standard
-a substance that is stable, non-hygroscopic (does not absorb moisture from air), and has a known composition (with preferably high molar mass)
-Ex. solid sodium hydroxide is hygroscopic and reacts slowly with CO2 in air to become sodium carbonate, so mass and composition changes when exposed to air
-In order to obtain NaOH solution of accurate concentration, we must first prepare solution of approximate concentration by titrating a primary standard
Desiccator
-a sealable container used to protect a dried object or chemical reagent from humidity
-Reagents for accurate analysis are dried in oven and kept in desiccator
-Contains drying agent (desiccant)
-Opened by slowly sliding cover to one side with one hand while anchoring it with other
Diffusion
if a solution contains regions of different concentrations of a species, the species will tend to move from areas of greater concentration to areas of lesser concentration
Occurs across a semipermeable membrane via pores in membrane (dialysis)
Diffusion rate using pH
rate = Δ[H+]ext /Δt
equilibrium pH
[H+eq] = total moles of H+ in solution / total volume of solution
