L.11 Solubility Flashcards
What is a Solution?
Solutions are homogenous mixtures composed of two or more substances
Four combinations of solutions
- Gasses into Liquids (carbonating soda)
- Liquids into Liquids (Ethanol in water)
- Solids into Solids (Metal alloys)
- Gases into Gases (“Mixtures” not solutions)
Definition of SOLVATION, also known as DISSOLUTION.
Solvent particles surround solute particles via electrostatic interactions in a process called solvation or dissolution.
What is HYDRATION?
When H2O is the SOLVENT in a Solution.
What are Intramolecular & intermolecular & forces?
Intramolecular forces
are the forces that hold atoms together within a molecule.
Intermolecular forces
are forces that exist between molecules.
Relative strength of the intramolecular forces ( 4 Forces)
Intramolecular force Basis of formation Relative strength
Metallic bond Metal cations to delocalized electrons 1. strongest
Ionic bond Cations to anions 2
Polar covalent bond Partially charged cation to partially charged anion. 3
Nonpolar covalent bond Nuclei to shared electrons 4, weakest
Relative Strenght of the Intermolecular Forces ( 3 Forces)
Intermolecular force Occurs between Relative strength
Dipole-dipole Partially oppositely charged ions. Strong
Hydrogen bonding. H atom and O, N/ or F atom Strongest of dipole-dipole attractions
London dispersion Temporary or induced dipoles Weakest
Happening between Solutes & Solvents
Explain what happens when dissolution is,
- Exothermic
- Endothermic
- No change
Exothermic; New interactions are Stronger. Favored at LOW Temp
Endothermic; New interactions are Weaker. Favored at High Temp
(Heat must be added “ Sugar + Hot Tea”)
No Change; New interactions = Old interactions
(enthalpy change close to 0, IDEAL SOLUTIONS)
The spontaneity if a dissolution depends on?
Enthalpy & Entropy
At constant Temperature and pressure, Entropy always increases upon dissolution.
Spontaneous RXNS = Decrease in Free Energy
(spontaneous messy room = no energy needed)
NON-Spontaneous RXNS = Increase in Free Energy
(non-spontaneous messy room = energy needed)
What is the definition of Solubility?
Molar Solubility?
Saturated Solutions?
Solubility is the maximum amount of solute that can be dissolved in a given solvent at a given temperature;
Molar Solubility - The amount of a compound that dissolves to make a saturated solution at equilibrium.
Above 0.1 M = Soluble
Below 0.1 M = Sparingly Soluble
Dilute Solutions
Concentrated Solutions
Saturated Solutions = In Equilibrium NO CHANGE IN FREE ENERGY
Aqueous Solutions 7 Rules.
Name 4 Important ones…
All Salts Containing
Ammonium NH4+
Alkali Metals Group 1 cations
Nitrate NO3-
Acetate CH3COO Anions
ALL WATER SOLUBLE
What are Complex Ions or Coordination Compounds?
These are composed of metallic ions bonded to various neutral compounds and anions, referred to as ligands.
CATION —- At least one electron pair donor, “Lewis Base” (LIGANDS)
Bonded by a coordinate covalent bond
- Coenzymes (vitamins)
- CoFactors EX: Cobalamin (B12) Co+ - bind other ligands or assist w/ electron tranfer
What is Chelation?
Some Complex Ions central cation can be bonded to the same ligand in multiple places “large organic ligands”.
Chelation therapy is used to sequester toxic metals, (lead, arsenic, mercury and even iron in high doses)
Percent Composition by Mass
For
- Aqueous Solutions & Solid-in-Solid Solution
Mass of SOLUTE / Mass of SOLUTION x 100%
Molality
For
- Boiling Point Elevation & Freezing Point Depression
Moles of Solute per Kilogram of Solvent
m = MOLES of SOLUTE / KILOGRAMS of SOLVENT
Mole Fraction
For
- Vapor Pressure Depression & Partial Pressure of gases in a system
Moles of Solute per Total Moles
XA = MOLES of A / TOTAL MOLES of ALL Species
Molarity
For
- Rate Laws, the Law of Mass Action, Osmotic Pressure, ph & pOH, Nernst Equation.
moles of SOLUTE per liters of SOLUTION
M = MOLES/ LITERS of SOLUTION
Normality
Is the Molarity of the Species of interest
For
- Acid-Base & Oxidation-Reductions
Number of Equivalents / Liters of Solution
Dilution
M1V1 = M2V2
Parts Per Million?
PPM = 10-6
One milligram of a substance per 1 Liter of solution
DENSITY OF WATER = 1g/mL
Sparingly Soluble Salts
- Low Solubility
- The degree of solubility is determined by enthalpy and entropy changes at a given Temperature and Pressure
MX Ksp = X2
MX2 Ksp = 4X3
MX3 Ksp = 27X4
Where X = Molar Solubility & there is no common ion effect in play
What is the Solubility Product Constant Ksp
Is the equilibrium constant for a dissociation reaction
Ksp Increases w/ Increasing Temperature NON-GAS SOLUTES
Ksp Decreases w/ Increasing Temperature GAS SOLUTES
Ksp Increases w/ Increasing Pressure GASES
Ion Product IP
IP = Ionic constituents at a given moment in time
Comparison of the IP to Ksp determines the level of saturation and behavior of the solution
IP < Ksp. Unsaturated Not at EQ
IP = Ksp Saturated EQ
IP > Ksp Supersaturated Beyond Saturation
What is the Formation or Stability Constant? Kf
is the equilibrium constant for complex formation, its value is usually much greater than Ksp.
- Formation of complex ions increases the solubility of other salt containing the same ions because it uses up all the products of those dissolution reactions, shifting the equilibrium to the right (opposite of the common ion effect)
The common ion effect
Decreases the solubility of a compound in a solution that already contains one of the ions in the compound
What is Colligative Property?
Name 4
Physical properties of a solution that depend on the concentration of dissolved particles rather than their chemical identity.
- Vapor Pressure Depression
- Boiling Point Elevation
- Freezing Poin Depression
- Osmotic Pressure
Raoults Law or Vapor Pressure Depression
More solute into Solvent = Decreases Vapor Pressure of Solvent
- Solute molecules block evaporation
- Does not affect condensation
- An overall net reduction in Vapor Pressure
PA = XA P*A
PA vapor pressure of solvent A
XA mole fraction of solvent A in solution
P*A pure state vapor pressure of solvent A
Boiling Point Elevation
non-volatile solute dissolved into a solvent to make a solution
The boiling point of the solution > boiling point of the pure solvent
Boiling point; the temperature at which the vapor pressure of the liquid id EQUAL to the ambient pressure
∆TB = i Kb m
∆TB change in boiling point
i Van’t Hoff Factor (number of dissociated ions)
Kb proportionality constant = is given
m molality
Freezing Point Depression
Solute Particles interfere with lattice arrangement of solventthus more energy is needed to be REMOVED from solution (lower T) in order tom solidify
- Water Freezing Point = 32F 0C 273
- For every mol of solute dissolved in 1 kg of H2O freezing point decreases by 1.86C
∆Tf = i Kf m
∆Tf Freezing point depression
i Van’t Hoff Factor (number of dissociated ions)
Kf proportionality constant
m molality
Osmotic Pressure
“sucking Pressure” generated by solutions, H2O drawn into solution
II = i M R T
II = osmotic pressure
i = Van’t Hoff Factor (number of dissociated ions)
M = Molarity
R = Ideal gas constant
T = Temperature