CHEM 1160

Non-electrolytes

(non-metals) do not break apart in solution

IMF vs Surface Tension

- The stronger the intermolecular forces, the higher the surface tension

IMF vs viscosity

- The stronger the intermolecular forces, the higher the viscosity

Equilibrium

- When vaporization and condensation rates become equal ( liquid to gas )

critical temperature

- the highest temperature at which the substance can be liquefied from the gas phase, regardless of pressure - At higher temperatures, the average kinetic energy of the gas molecules is so high , it overcomes the intermolecular attractive forces that cause liquefaction - Therefore at temperatures above the critical temperature, the gas cannot be condensed into the liquid phase, despite increases in pressure

Hydrogen Bond

A particularly strong type of dipole-dipole attraction that occurs when a hydrogen atom is bonded to a small, highly electronegative atom (including F, O, and N). The attraction is between the hydrogen atom and the F, O, or N atom on the neighboring molecule. For example, water molecules will exhibit hydrogen bonding.

Equilibrium process in a saturated solution

A saturated solution represents the equilibrium balance between the rates of dissolution of solid solute molecules and crystallization of dissolved solute. At equilibrium, the rate of crystallization is exactly equal to the rate of dissolution

" like dissolves like " in terms of intermolecular force

A solute will be most soluble in a solvent that generates intermolecular forces similar in strength to its own

Hydrogen Bonding

A special type of dipole-dipole interaction between a hydrogen atom that has a partial positive charge and a small, highly electronegative atom on another molecule (such as N, O, or F)

How does electron density distribution of a molecule change when the molecule approaches a dipole or charged particle.

As the molecule approaches the polar molecule or ion , the electron density distribution shifts. If the approaching charge is negative, the electron density distribution shifts so that the electron density is highest in the parts of the molecule that are farthest from the approaching charge. If the approaching charge is positive, the electron density distribution shifts so that the electron density is highest at the parts of the molecule that are closest to the approaching charge.

What intermolecular forces can exist in a gaseous sample of HCl

Dipole - Dipole London Dispersion

Substances when dissolved in water, undergo a physical or chemical change

Electrolyte

Solid to liquid to gas

Energy (heat) is required to change from solid to liquid to gas; more energy needed if strong intermolecular forces are present

_________ is the reason substances mix homogeneously

Entropy

Solubility

Extent to which a solute may be dissolved in water, or any solvent - Heat helps most solids dissolve - Heat DOES NOT help gasses dissolve - Pressure helps gasses dissolve

Describe how hydrogen bond attractions affect the physical properties of a compound

HB attractions between molecules of a substance lead to a high boiling point, surface tension, specific heat, cohesion, and capillary action.

Classify hydrogen bond attraction as a type of intermolecular force.

Hydrogen bond attraction is a type of dipole-dipole force.

Identify the types of molecules or atoms that exhibit hydrogen bond attractions.

Hydrogen bond attraction occurs when an atom with an extremely high electronegativity is bound to a hydrogen atom.

Dipole- or Ion- Induced Dipole

Induced dipoles occur when an ion or a polar molecule induces a nonpolar species to become polar . Charges can be induced in a nonpolar species when a nearby ion or dipole disrupts the electron arrangement of the nonpolar species. This disruption induces the formation of charges in the formerly nonpolar species. This creates a transient electrostatic attraction between the partial charges of the inducing species, and the formerly non-polar species

___________ _______ influence the mixing of substances

Intermolecular forces

IMF vs. state of matter

Intermolecular forces dictate the state of matter of molecules ion-dipole, H-bonding, dipole-dipole, and dispersion

Electrolyte

Ionic compounds (metal and non-metal) that break apart into individual ions in solution

boiling point elevation ( non - electrolyte )

Kb = 0.512 *C/m for water as solvent

freezing point depression

Kf = 1.86 *C/m for water as solvent

Numerous solution concentrations are used based on scientific discipline

Molarity (mols/liter) Molality (mols/kg)

Molality ** MEMORIZE **

Mols */. Kg

Molarity ** MEMORIZE **

Mols */. L

Miscible

Mutually soluble in all proportions; typically refers to liquid substances (sometimes gases and solids)

colligative properties

Properties of solutions, such as vapor pressure lowering, freezing point depression, boiling point elevation, and osmotic pressure, that are affected only by the number of solute particles dissolved and not by their chemical identities.

osmotic pressure

R = 0.08206 L*atm / K*mol

Sublimation

Solid directly to gas

Heat of fusion ( /\Hfus )

Solid to liquid ( melting )

Solutes added to solvents form_________

Solutions

_________ form when things mix homogenously

Solutions **** Solute (minority) into solvent (majority)

boiling point

The boiling point of a solution increases directly as a function of the number of moles of solute present in a given mass of solution. This relationship is expressed mathematically by the following equation. ΔTb = Kb x m - ΔTb is the boiling-point elevation of a solution - m is the molality of solute particles in solution - Kb is the molal boiling-point-elevation constant

Electrolyte vs. non- electrolyte in colligative properties

The colligative properties of a solution depend on the quantity of particles dissolved in solution. Therefore, the colligative properties of an electrolyte solution differ by a factor of n compared to colligative properties of a solution made from a nonelectrolyte of equal molar quantity, where n is the number of ions making up the electrolyte.

Ion - Dipole

The electrostatic attraction between an ion and the opposite partial charge on a nearby dipole

Dipole- Dipole

The electrostatic attraction between the opposite partial charges of two dipoles

Dipole - Dipole Attraction

The electrostatic attraction between two permanent dipoles. The attraction occurs between the partial positive end of one polar molecule and the partial negative end of another polar molecule. For example, carbon monoxide molecules will exhibit dipole-dipole forces on each other

why does hydrogen bonding results in a higher boiling point of a substance.

The energy required to disrupt hydrogen bonding is higher than the energy required to break weaker types of interactions, such as van der Waals forces, which results in a higher boiling point.

Describe hydrogen bond attractions between water molecules in the liquid phase

The partial charge on a water molecule attracts the opposite partial charge on adjacent water molecules

Describe the property of the water molecule that leads to hydrogen bond attractions

The water molecules have permanent dipoles with greater partial charge distribution due to the higher electronegativity of the oxygen atom and the location of the nonbonding electrons.

London Dispersion Forces

Very weak electrostatic attractions that occur due to the random electron motion within all substances, including those that are nonpolar. When the electrons within a molecule or atom randomly move to the same area of its electron cloud, that molecule or atom will adopt a transient charge. This charge can include the formation of an opposite charge in nearby atoms or molecules, creating a brief electrostatic attraction between the two species

Dispersion Force

Very weak electrostatic attractions that occur due to the random electronic motion within all substances, including those that are non-polar. When the electrons within a molecule or atom are distributed asymmetrically about the nucleus, that molecule or atom will adopt a temporary , instantaneous dipole. The presence of this dipole can then distort the electrons of a neighboring atom or molecule, producing an induced dipole. These two rapidly fluctuating dipoles thus result in a brief electrostatic attraction between the two species. These forces are stronger in larger and heavier atoms and molecules. For example, dispersion forces between iodine molecules will be stronger than dispersion forces between fluorine molecules.

Molar Mass ( MM ) =

g */. mol

Pressure helps what dissolve

gases

van't Hoff

i = 1 for non- electrolytes i > 1 for electrolytes

heat of vaporization ( /\Hvap )

liquid to gas

Composition of Covalent-network solids

made up of a network of atoms bonded together with covalent bonds

Composition of Metallic solids

made up of metal atoms held together with metallic bonds

Composition of molecular solids

made up of molecules joined together by intermolecular forces

Composition of Ionic solids

made up of oppositely charged ions joined by ionic bonds

" like dissolves like " in terms of solubility

means polar solutes are more soluble in polar solvents and nonpolar solutes are more soluble in nonpolar solvents

Entropy

measure of energy dispersal in a system

Ionic compounds

metal and nonmetal

Solubility of gasses increases as..

pressure increases

Temperature helps what dissolve

solids

Solubility of gasses in liquids decreases as..

temperature increases

a. Use van't Hoff when the problem:

§ Mentions " ionic solution " § States " assume complete dissociation of solute " § Gives an value in the problem