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Kaplan General Chemistry > L.11 Solubility > Flashcards

L.11 Solubility Flashcards

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1
Q

What is a Solution?

A

Solutions are homogenous mixtures composed of two or more substances

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2
Q

Four combinations of solutions

A
  1. Gasses into Liquids (carbonating soda)
  2. Liquids into Liquids (Ethanol in water)
  3. Solids into Solids (Metal alloys)
  4. Gases into Gases (“Mixtures” not solutions)
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3
Q

Definition of SOLVATION, also known as DISSOLUTION.

A

Solvent particles surround solute particles via electrostatic interactions in a process called solvation or dissolution.

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4
Q

What is HYDRATION?

A

When H2O is the SOLVENT in a Solution.

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5
Q

What are Intramolecular & intermolecular & forces?

A

Intramolecular forces

are the forces that hold atoms together within a molecule.

Intermolecular forces

are forces that exist between molecules.

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6
Q

Relative strength of the intramolecular forces ( 4 Forces)

A

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

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7
Q

Relative Strenght of the Intermolecular Forces ( 3 Forces)

A

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

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8
Q

Explain what happens when dissolution is,

  1. Exothermic
  2. Endothermic
  3. No change
A

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)

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9
Q

The spontaneity if a dissolution depends on?

A

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)

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10
Q

What is the definition of Solubility?

Molar Solubility?

Saturated Solutions?

A

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

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11
Q

Aqueous Solutions 7 Rules.

Name 4 Important ones…

A

All Salts Containing

Ammonium NH4+

Alkali Metals Group 1 cations

Nitrate NO3-

Acetate CH3COO Anions

ALL WATER SOLUBLE

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12
Q

What are Complex Ions or Coordination Compounds?

A

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
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13
Q

What is Chelation?

A

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)

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14
Q

Percent Composition by Mass

A

For

  • Aqueous Solutions & Solid-in-Solid Solution

Mass of SOLUTE / Mass of SOLUTION x 100%

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15
Q

Molality

A

For

  • Boiling Point Elevation & Freezing Point Depression

Moles of Solute per Kilogram of Solvent

m = MOLES of SOLUTE / KILOGRAMS of SOLVENT

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16
Q

Mole Fraction

A

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

17
Q

Molarity

A

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

18
Q

Normality

A

Is the Molarity of the Species of interest

For

  • Acid-Base & Oxidation-Reductions

Number of Equivalents / Liters of Solution

19
Q

Dilution

A

M1V1 = M2V2

20
Q

Parts Per Million?

A

PPM = 10-6

One milligram of a substance per 1 Liter of solution

DENSITY OF WATER = 1g/mL

21
Q

Sparingly Soluble Salts

A
  • 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

22
Q

What is the Solubility Product Constant Ksp

A

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

23
Q

Ion Product IP

A

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

24
Q

What is the Formation or Stability Constant? Kf

A

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)
25
Q

The common ion effect

A

Decreases the solubility of a compound in a solution that already contains one of the ions in the compound

26
Q

What is Colligative Property?

Name 4

A

Physical properties of a solution that depend on the concentration of dissolved particles rather than their chemical identity.

  1. Vapor Pressure Depression
  2. Boiling Point Elevation
  3. Freezing Poin Depression
  4. Osmotic Pressure
27
Q

Raoults Law or Vapor Pressure Depression

A

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

28
Q

Boiling Point Elevation

A

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

29
Q

Freezing Point Depression

A

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

30
Q

Osmotic Pressure

A

“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

Kaplan General Chemistry (10 decks)

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