Chem unit 3

Two types of attractive forces

intramolecular and intermolecular

What are intramolecular forces?

Forces that hold atoms together within a molecule

2 types of intramolecular forces

covalent and ionic bonds

What force is shown?

Intramolecular force

What are intermolecular forces (IMF)?

Forces that attract separate molecules to each other

4 types of IMFs in order of strongest to weakest?

Ion-dipole, hydrogen bonding, dipole-dipole, dispersion forces

What force is shown?

IMF

When water boils what force do you overcome?

intermolecular attractions between water molecules

Dispersion force explanation

found in all substances and arise from temporary polarization of electrons

What IMF is this?

Dispersion

What force do non-polar molecules only have?

Dispersion

Dipole-dipole explanation

electrostatic force between partially positive end of one polar molecule and partially negative end of another

What IMF is this?

Dipole-dipole

Hydrogen bonding explanation

only can be formed by N-H, O-H, or F-H bonds due to having larger electronegativity values.

In hydrogen bonds rank the electronegativities from lowest to highest (HF, NH3, H2O)

NH3 H2O, HF

What IMF is this?

Hydrogen

Ion dipole explanation

occurs when salt dissolves in water causing its ions to strongly attract water molecules. In short they are attractions between ions and polar water molecules

What IMF is this?

ion-dipole

Boiling point definition

The temperature at which a liquid turns into gas

90iop;n Boiling point trend

Stronger IMFs = higher boiling point

Vapor pressure definition

the pressure exerted by vapor molecules above a liquid when evaporation and condensation occur at equal rates

Vapor pressure trend

stronger IMFs = lower vapor pressure

Rate of evaporation definition

how quickly a liquid turns into a gas at its surface

Rate of evaporation trend

Stronger IMFs = slower evaporation

Heat of vaporization definition

energy required to convert one mole of liquid into gas at its boiling point

Heat of vaporization trend

stronger IMFs = higher heat of vaporization

Surface tension definition

the tendency of a liquid surface to resist being stretched or broken because of attraction between its molecules

Surface tension trend

Stronger IMFs = higher surface tension

Capillary action definition

ability of a liquid to rise or fall in a narrow tube due to adhesion and cohesion

Viscosity definition

A liquid’s resistance to flowing

Viscosity trend

Stronger IMFs = higher viscosity

Which values have inverse relationship with IMF

Rate of evaporation, vapor pressure, gas ideality

Name 4 types of crystalline solids

Ionic solid, metallic solid, molecular solid, covalent networks

Ionic solid definition

Bond between metals and nonmetals

What are ionic solids held together by?

electrostatic attractions

Molecular solid definition

bond between nonmetals only

What are molecular solids held together by?

London dispersion forces, dipole-dipole, or hydrogen bonds

Covalent network (atomic solids) definition

bond between nonmetals only

What are covalent networks held together by?

sheets of hexagonal structure by covalent bonds held by weak London forces.

Metallic solids definition

metals only

What are metallic solids held by?

metallic bonds

Ideal gas law definition

PV=nRT

T/F do real gases deviate from ideal behavior?

True

Why do real gases deviate from ideal behavior?

They have a finite volume and intermolecular forces acting between the particles

At what conditions do real gases exhibit nearly ideal behavior?

high temperatures and low pressures

What is Van Der Waals equation?

Label blue and yellow sections

blue is metal, yellow is non metal

Random motion definition

Gases consist of a large number of molecules/atoms that are in continuous random motion

Negligible molecular volume definition

The combined volume of all the gas molecules is negligible relative to the total volume in which the gas is contained.

Elastic collision definition

Energy can be transferred between molecules during collision but as long as temperature remains constant the average kinetic energy of the molecules does not change with time

Average kinetic energy is proportional to temperature definition

the average kinetic energy of the molecule is proportional to the absolute temperature.

T/F at any given temperature do the molecules of all gases have the same average kinetic energy?

True

What does no IMF mean?

no attraction between particles

T/F in a sample of gas when all the molecules have same KE they all have the same speed

False

Maxwell-Boltzmann distribution

molecules in a substance move at different speeds and the distribution shows how many molecules have each amount of energy. As temperature increases molecules have more energy on average, so more can overcome intermolecular forces and escape a liquid.

What does the top of the curve mean

it the speed at the top of curve is called the most probably speed because the largest number of molecules have that speed.

What are the two equations of K.E?

What is k in the K.E equation?

k= Boltzman’s constant when you think about the energy of a single atom.

What are the avg velocity equations?

What is the combined equation for avg velocity of the particles?

What gases move slower?

slower gases

What does speed depend on?

molar mass and temperature

Diffusion definition

intermingling of gases due to their random motion

Effusion definition

escape of gas particles through a tiny hole

Graham’s law of effusion explanation

Lighter gases escape through a tiny hole haser than heavier gases. Rate of effusion is inversely proportional to the square root of the gas’s molar mass

Graham’s formula

Boyle’s Law

Charles’s Law

Avogadro’s Law

Gay-Lussac’s Law

Combined Gas Law

Ideal Gas Law

Density and Gas Law

Density law

Mole formula

n=m/M

What makes IMF stronger?

larger size or higher force of IMF

What makes something less ideal?

being very large or having strong IMF

What does b mean in Van der Waals?

Volume occupied by molecules

What does a mean in Van der Waals equation?

attraction between molecules