Lernen: Chem 101 Exam 3 UNC CH

Does BP increase or decrease as size/# of electrons increases?

increase, more energy levels and pull from nucleus makes it harder to separate bonds and form gas

does BP increase of decrease as polarizability increases?

Increase, high polarizability means tighter bonding, and therefore more energy to separate bonds during boiling.

intramolecular forces are ______ molecules

in

intermolecular forces are ______ molecules

between

is PE in attraction + or -

-

is PE in repulsion + or -

+

Explain the Eel equation (how do you use it?)

come bck to this later

LDFs ______ as polarizability increases

increases

LDFS _____ as size increases

increases

as LDFs increase, boiling point _______

increases

for LDFS, what is the order of importance for determining higher BP?

1. size

2. polarizability

3. shape

more spread out molecules/more branching (less circular) have ______ boiling points

higher

what causes LDFs?

temporary dipoles, exist in every molecule/atom. An attraction between + and - charges of molecules, usually break when given too much distance, weakest IMF

structural/constitutional isomer

same molecular formula/mass, but different shape

as SA/branching increases, BP increases, LDFs increase

viscocity

the resistance to flow a liquid has, thickness. unit is cP

as size/# of electrons increases, viscosity _________

increases

as IMFs increase in strength, viscosity _________

increases

Dipole-Dipole forces

occur between polar molecules with a permanent dipole

LDFs

occur between temporary dipoles in ALL atoms/molecules

as dipole dipole force increases, BP _________

increases

as polarizability/difference in electronegativity increases, the strength of the dipole, and therefore the DD forces ________

increase

polar bonds

covalent bond witch uneven electron distribution, has a charge.

forms TEMPORARY dipoles

polar

molecule with a difference in electronegativity (permanent dipole) and an asymmetrical structure

as size/mass increases, DD forces ______

size has no affect on DD forces silly!! :p

How do you know which IMF to use to decide higher BP?

go down the chain of strength, if the strength of one IMF is the same or VERY similar between the compared molecules, go onto the next strongest.

Hydrogen Bonding

H bonded to a N/O/F lone pair, type of DD, intermolecular, ONLY between polar molecules (have a permanent dipole)

must be bonded to a N/O/F both within its own molecule and to the other molecule

Can a HB exist between itself as well as a different molecule?

YES, molecules that can form HBs with themselves must have H bonded to N/O/F WITHIN the molecule, while in order to form HBs with some other molecules, a molecule only needs a HB donor or acceptor

HB donor

H atom bonded to LP of N/O/F

HB acceptor

LP of N/O/F

as the number of possible H bonds increases, the BP ________

increases

this occurs when a molecule has an = # of donors/acceptors (or slightly greater as long as its not below =)

Rank the IMFs in terms of strength (and then their subfactors affecting their own strength if u want)

1. Ionic

2. Hydrogen Bonding (# of possible HBS, distance but we never talked about this)

3. DD forces (difference in electronegativity -> size but it's like never applicable)

4. LDFS (size, polarization/difference in electronegativity, SA/branching/structure)

Ionic compound

metal + nonmetal/polyatomic ion

As a general trend in Hydrogen Bonding, as size/mass of a molecule increases, BP ______

increases

ion-dipole interaction

ion + polar molecule

a la NaCl in water

Which is stronger, I-D interactions of HB?

I-D interaction

Why are ID interactions stronger than DD forces?

because DD forces involve atoms with PARTIAL charges, which ID interactions result in the full loss/gain of one or electron as create a non-partial charge of at least 1+/-

What are the strong acids?

HCl, HBr, HI, HNO3, H2SO4 (first proton), HClO4

What are the strong bases?

NaOH, KOH, RbOH, LiOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

conjugate acid

base + 1 H atom

is water an acid or base?

water can be both an acid and a base, as it has H donors and O LP acceptors

strong acids/bases are _______ electrolytes

strong

the more H donors a compound has, the _______ an acid is

stronger, so when an acid like H2SO4 looses its first proton, it becomes much weaker, as it can only bond with one water molecule instead of two

Bronsted-Lowry acid and base

acid: donates a H+ ion

base: accepts an H+ ion

when does OH- act as a base?

when it is bonded to a metal/positive ion

What is the density formula? when do you use it?

M1V1 = M2V2

used when you are trying to find an aspect of concentration when diluting a solution

electrolyte

disassociates into ions in water

strong ones disassociate completely

electrolytes are ionic compounds, acids, or bases

ppm

parts per million

1 ppm = 1g/1,000,000 g water

how do you find bond order in MO theory?

.5(# of bonding e- - # of nonbonding e-)

as bond order increases, bond length _______

decreases

MO hybrid orbitals are _______ in energy than the parent orbitals they form from

lower

Hunds Rule

electrons don't pair up until filling all orbitals of the same energy level

applies to MO orbitals

general MO rules

the number of MO orbitals formed is equal to # of parent orbitals

Hunds rule applies

electrons are assigned to orbitals of successively higher energy

lower in energy than parent orbitals

combustion reaction

hydrocarbon + oxygen (usually gas) -> CO2, H20, heat

What are water's unusual properties? What causes them?

high BP due to strength of HBs

high surface tension due to strength of HBS

Denser as a liquid than solid due to solid water having a very open hexagonal structure weakening the strength of the HBs

flows against gravity due to its high adhesive properties

adhesion

ability to stick to surfaces, represented by convex meniscus

cohesion

ability to stick to self, represented by concave meniscus

triple point

where three states exist at equilibrium

critical point

point where liquid and gas become undistinguishable

supercritical fluid

indistinguishable liquid and gas, past critical point

gas to solid phase change

deposition

solid to gas phase change

sublimation

as polarity increases, solubility in water _______

increases

how does the ability for HB affect solubility

increases it, more i

Like dissolves like

polar substances like to dissolve in polar substances, same for nonpolar

can nonpolar solutes dissolve in polar solvent?

they don't usually, but could due to dipole-dipole interactions

why dont most nonpolar solutes disolve in polar solvents

because in most cases the strength of the interactions between the non-polar molecules itself is higher than the strength of the solute-solvent interaction

as the length of the carbon chain increases, solubility ______

decreases, as does dipole dipole strength