Exam 2

Question 1

Frequency

Answer 1

Speed of light = frequency * wavelength; 2.998 *10^8m/s = speed of light

Question 2

Energy of a photon

Answer 2

E = hv

E = energy, v = frequency, h = 6.626*10^-34J (Planck’s Constant)

v = speed of light / wavelength

Question 3

Photoelectric effect

Answer 3

When light has enough energy to break electrons free from metal. If an electron picks up enough energy, it can break free from the surface of the metal, the more energy given to the electron the faster it will travel after it leaves the metal.

Below a threshold frequency no electrons are emitted, # of electrons is independent of frequency but increases with increasing light intensity. The energy of the released electrons increases linearly with frequency after the threshold, but is independent of the intensity of light.

Question 4

Energy Levels

Answer 4

increases from E1->E4, photons are emitted when going from higher energy states to lower, (E3 to E2 has higher wavelength than E3 to E1)

Question 5

Electron Configuration

Answer 5

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

reference chapter 6 slide deck 7 for picture

Question 6

Quantum Numbers

Answer 6

n, L, m

Principle quantum number: n = number of shells
L = number of subshells (0 - n-1) can have as many as the number of shells (n)
Magnetic quantum number: m = absolute value less than or equal to L (can be positive and negative
Spin quantum number: ms = +1/2 or -1/2, determines number of electrons that can occupy an orbital

Pauli exclusion principle: no two electrons of the same atom can have the same set of quantum numbers, first three can be the same but then the spin must be different

Question 7

Atomic Radius

Answer 7

Increases towards the bottom left of the periodic table

Question 8

Ionization Energy

Answer 8

increases towards the top right of the periodic table; higher energy means it takes more energy to loose electrons

Question 9

Electronegativity/Polar Bonds

Answer 9

the attraction of an atom for the shared electrons in a covalent bond, the higher the value, the more likely an element will attract extra electron density during compound formation

the more electronegative element has increase of electron density giving it partial negative charge, other element has partial positive charge

if electronegativity is 0 bond is covalent, otherwise polar covalent; if electronegativity is >2 = Ionic

Question 10

Lewis Structure

Answer 10

find total number of electrons, put more electronegative element in the middle (usually written first in formula), place single bonds between all connected atoms, place on outside atoms then central, place them in lone pairs to satisfy octet rule (sulfur and phosphorus can break octet rule), if octet rules are not satisfied, move lone pairs into bonding positions to satisfy them, resonance structures are when the lone pair can be changed from multiple atoms to satisfy octet rule and are represented with dual facing arrows

Question 11

Molecular geometry

Answer 11

Chapter 7 slide deck 5

Question 12

Sigma Pi bonds

Question 13

intramolecular forces

Answer 13

Vapor pressure: molecules at the surface of a liquid that will pass into gas phase; increase with temperature, strong intermolecular force = lower vapor pressure, high vapor pressure = volatile (higher means they evaporate more easily)

Normal Boiling Point: temperature where vapor pressure = 1 atm

Surface Tension: reaction to imbalance in attractive forces on the surface from the bulk of liquid; cohesion = liquid-liquid, adhesion = liquid-solid

Question 14

Is diamond or graphite a crystalline structure

Answer 14

diamond

Question 15

band gap diagrams

Answer 15

for metals the conduction band is next to the valence band and the energy to jump them is minimal; semi conductors have slight band gap and takes some energy to jump; insulators have very large band gap and take a very large amount of energy to jump

Question 16

polymers

Answer 16

giant molecules constructed by sequentially stringing together smaller molecules called monomers. Monomers containing one or more double bonds undergo free radical addition reactions to form addition polymers. This occurs through initiation, propagation, and termination

degree of polymerization = molar mass polymer / molar mass monomer

condensation polymers are formed when monomers react and produce water or another small molecule

copolymers are made up of more than one type of monomer: alternating, block, random, graft

thermoplastic: melt/deform upon heating
thermosetting: maintain strength

Question 17

Energy change in a system

Answer 17

E= q + w
when E is negative = energy is released
when E is positive = energy is absorbed

Question 18

Laws of thermodynamics

Answer 18

1. energy is conserved, transformed from one form to another, but not created or destroyed. Energy of system + energy of surrounding = energy of universe
2. it is impossible to convert heat completely to work

Question 19

Specific Heat

Answer 19

q = mcDELTA(T); where m is mass and c is specific heat

Question 20

Molar heat capacity

Answer 20

q = ncDELTA(T); where n = moles and c = heat capacity

Question 21

Hess’s Law

Answer 21

Enthalpy change for any process is independent of the particular way the process is carried out

H=sum of vdeltaHproducts - sum of vdeltaHreactants

Question 22

(Sign of) Entropy

Answer 22

measurement of disorder

more probable arrangements have higher entropy

Question 23

(Sign of) Enthalpy

Answer 23

conditions under which heat flow

H=E+PV

when h is negative = exothermic, releases heat
when h is positive = endothermic, absorbs heat

heat of vaporization: heat required to convert liquid to gas (endothermic)
heat of condensation: heat released to convert gas to liquid (exothermic)

H = number of moles * heat for phase change

if more bonds form than break = exothermic
if more bonds break than form = endothermic

Question 24

Aufbau Principle

Answer 24

filling of orbitals starting with the lowest energy and proceeding to the next highest energy level once full

Question 25

Hund’s Rule

Answer 25

within a subshell electrons occupy orbitals individually with parallel spins wherever possible

Question 26

Gibbs free energy

Answer 26

predicts is a process is spontaneous

G=H-TS