AP CHEM UNIT 3 STUDY GUIDE

motion of a gas

free to move, fast

motion of a liquid

has motionn / medium motion

motion of a solid

little to no motion

order of a solid

very orderly/ particles close together

order of a liquid

had order, typically takes shape of its container

order of a gas

no order at all, free to move however

empty space of gas 

a lot of empty space 

empty space of a liquid

has some empty space

empty space of a solid

very minimal empty space

energy of a gas

high

energy of a liquid

medium

energy of a solid

little to no energy

Ion-dipole

STRONGEST IMF

interactions between ions and polar molecules 

hydrogen bond

2ND STRONGEST IMF

occurs between hydrogen (duh) and either N, O, F since they are most electronegative

dipole-dipole

MIDDLE STRENGTH IMF

interactions between two polar molecules

dipole induced dipole

interactions between a polar and non-polar molecules

2ND WEAKEST IMF

london dispersion forces

interactions between two non-polar molecules

WEAKEST IMF

Why are IMFs with ions much stronger than IMFs with dipoles

The ions have a permeant, complete charge, while dipoles only have a slight and incomplete charge. If charges are stronger, so will the IMFs

why do molecules have dipole moment?

They both have slight opposite charges, meaning they will be more attracted to one another

Why do molecules that have a dipole moment have attractive forces?

They all have slight + and - charges, allowing for attraction between one another

What is the trend for polarity and boiling point?

Polar molecules have a higher boiling point because of stronger IMFs

What intermolecular forces are involved in h-bonds?

really large partial charges

What happens to boiling points as you move down the periodic table?

The boiling points become more similar as you move downward in periods because of a larger electron cloud from being larger/having more electrons present

How does the strength of hydrogen bonds compare to the strength of intramolecular covalent bonds within molecules?

It is much weaker than a covalent bond (the bonds would break if the opposite was true)

What factors increase the likelihood of such an instantaneous dipole developing

Larger electron clouds (more electrons)

Increased contact areas

If a molecule has an instantaneous dipole, what effects will that have on nearby molecules? 

They will also form temporary dipoles

What is the trend in boiling points for halogen gases and noble gases?

They increase as you move down the periodic table because of more e- in more electron shells

Crystalline Solids

Regular arrangements of atoms or molecules in a solid

Amorphous solid

Considerable disarray in structures

Structures of solids are determined through..?

x-ray defraction

Metallic solids

Have metal atoms in its lattice points

bonding — delocalized via sea of electrons

High melting point

High malleability

High conductivity

Network Covalent solid

Nonmetal atoms at its lattice points

Directional covalent bonds 

High melting point

Not malleable

Conductivity varies

Molecular solids

Discrete molecules at lattice points

Dipole-Dipole and London dispersions for interactions

Low melting point

no malleability or conductivity

Ionic solids

Ions in lattice points

Ionic bonding

high melting point

low malleability

low conductivity

Group 18 Solids

Group 18 atoms in lattice points

london dispersion forces

very low boiling point

no malleability or conductivity

How is melting point related to the strength of an IMF

Stronger IMFs require more energy to be distrupted

Why does only one type of solid have high conductivity?

Ions in ionic soluds are unable to be free so it cannot conduct electricity, metallic solids have a sea of electrons that allow for conduction of electivity.All others consist of nonmetals

What do network solids have low conductibility

They have hard structures and complex compositions, they are also non-metals

Why are ionic solids brittle

Like charges will align when shattered, repulsion of like charges

Diamond and graphite are both netowrk soldus of carbon atoms. What are the differences in the C-C bonding?

The c-c bonding allows forr stacking through weaker bonding in layers (graphite)

Diamonds have a etrahedral shape that is arranged in a way to keep its shape

How does the difference in bonding in diamond and grpahite lead to diffeences in hardness?

Diamond’s shape causes for it to be very hard while the layers in graphite allow for the laers to break off and make it brittle

Molecules in lattice points in molecular solids have _____ bonds wihtin each molecule

covalent

Surface tension

energy required to increase the surface area of a liquid

Cohesion

IMFs between molecules in a liquid

Adhesion

measure of strengths of IMFs between molecules of a liquid and their container

Surface tension is responsible for…

formation of spherical shapes

Surface tension varies on…

IMFs and size!

Glass contains many oxygen atoms with partial negative charges, what happens when a water molecule comes in contact with glass?

partial pressure of H (partially positive) will be attracted to the glass

What happens when water is added to a glass graduated cylinder? What happens with adhesion and cohesion?

Adhesion increases, cohesion decreases

Compare relative height of liquid: hexane vs water

water has a meniscus, while hexane does not

Compare relative height of liquid: water vs soap solution

water has a meniscus, soap will not

Compare relative height of liquid: fat tube vs skinny tube

skinny will be higher

Compare relative height of liquid: dense liquid vs not dense liquid

not dense liquid

Capillary action

movement of liquid through narrow space, driven by adhesion and cohesion

Viscosity

Measure of liquid’s resistance to flow

What impacts viscosity?

Thickness of a liquid

Chemical makeup/composition

IMFs

Tempuratre

How do n-pentane and neopentane (NEO?? SPAMTON NEO???) differ in their boiling points through their structures (despite having the same molecular formula?)

One is much stronger than the other based on its structure. N-pentane to be closer together

During which process does the energy of the system increase?

Melting and vaporization sublimation

During which process does the energy of the system decrease on a heating curve?

condensation, freezing, deposition

Can a system be in more phase at one time?

Yes, liquid in process of freezing, solid in process of melting, boiling a substance

vapor pressure

individual molecules that contain enough energy to move as a vapor not through heating

How is vapor pressure measured?

Torr in barometers

What quanities are necessary for measuring gasses?

constant movement/motion

volume

tempurature

energy

How are force and pressure related ?

P = nRT/v

P = F / A

How do we measure gasses?

Nanometer and barometer

How does a barometer work?

Measures atmospheric pressure using Hg, since it is extremely dense, with the movement of Hg indicating the pressure.

How does a nanometer work?

Both sides of the nanometer are equal means that there is equal pressure

If atm is stronger, the height of Hg would be more toward the left

if the gas pressure is stronger, the Hg would be more toward the right

What is the relationship between pressure and volume in a gas?

Pressure decreases when volume increases, pressure increases when volume decreases

INVERSELY PROPORTIONAL

What is the relationship between volume and # moles of particles when P and T are constant?

More area = more moles, proportional

What is the relationship between volume and temperature when pressure is constant?

Heat makes volume expand, volume condenses when gas is cooled

How does Celcius differ from K?

Kelvin has a point known as “absolute zero” which C does not, 0 C does not align with absolute 0

Ideal Gas Law

Each particle is assumed to have whole container to move freely in

Molecules contain no volume and occupy 0 volume

Particles will not change motion when interacting with other gas particles

Assumed no IMFs

All collisions are elastic (do not cause energy loss)

STP (standard temp of pressure)

One mole of ideal gasses contain volume of 22.4 L of STP

What is the equation of the partial pressure?

Ptotal = P1 + P2 + P3

What is the equation for mole fraction?

xi = moles of gas / total # moles

Pi = Pt(Xi)

What does the average speed of a gas particle depend on?

Gas type that makes up the sample

Tempurature

Size

What are the four postulates of the kinetic molecular theory?

Particles are free to move in container/given space

Particles are in constant motion, collisions with wall = same

Exert no forces on one another, no IMFs

Average kinetic energy at particles is proportional to the Kelvin temperature of the gas

As the walls of the container move further apart….

pressure will decrease

As temperature increases…

pressure increases more collisions from speeding up and exerts more force when it hits the wall

If temperature increases but pressure remains constant…

The volume must increase

As the number of particles in a container increases…

the pressure will also increase, each individual particle will have the same contribution

What is temperature measuring?

the average kinetic energy

What is the equation for calculating KE?

KE = ½ mv²

What is the relationship between speed and temperature of a gas?

T is proportional to ½ mv²

What is the difference in distribution in speed in a Maxwell-Blotzmann graph indicate? 

They are skewed based on temperature or type of gas

What happens to the peak speed as temperature increases in a Max-Boltz diagram

They shift rightward

What happens to the number of molecules at the peak speed as temperature increases in a Max-Boltz diagram?

The number of molecules decreases by being more spread than concentrated in specific areas.

What happens to the width of distribution as temperature increases in a Max-Boltz diagram?

They become much greater/spread out

What molecules have the highest average speed in a Max-Boltz diagram with different gases with the temp held constant?

The lightest/molecules with lowest mass have the highest speed, the heaviest molecules have the lowest speed

What two postulates from the Kinetic Molecular Theory are modified in real gasses?

No IMFs and negligible volume

Real gasses that behave closest to an ideal gas have…

high temps

low pressure

small particles

weak IMFs

In a PV/RT graph with gasses at different temperatures, why would the gas have a larger deviation at a higher pressure

since the number of moles increases

In a PV/RT graph with gasses at different temperatures, why do the gases have a smaller deviation at higher temperatures?

There are stronger IMFs

In a PV/RT graph with different gasses at the same temperature, why do the lines start from a similar point?

They have an assumed infinite volume

In a PV/RT graph with different gasses at the same temperature, do the gases have different curves?

The IMFs are different in strength, hence fewer collisions and different pressures

Which gas would be more likely to behave like an ideal gas based on IMFs? He vs Xe

He (experiences weaker IMFs)

Which gas would be more likely to behave like an ideal gas based on IMFs? Ne vs H2O

Ne

Which gas would be more likely to behave like an ideal gas based on IMFs? NH3 vs CH4

CH4 (non-polar, experiences LDF)

Which gas would be more likely to behave like an ideal gas based on volume? He vs Xe

He (smaller)

Which gas would be more likely to behave like an ideal gas based on IMFs? Ch4 vs H2

H2