CHE 002B

(change) U

change in internal energy

first law of thermodynamics

energy cannot be created or destroyed, only converted

(change) U formula

q+w

q=heat

w=work

heat

energy relative to temperature

heat: if temp is higher, speed is

higher

heat: if temp is lower, speed is

decreased

endothermic

heat absorbed by temp

exothermic

heat released by temp

work formula

\-P(change)V

\-w

work done BY system, on surrounding

\+w

work done ON system, by surrounding

state functions

U, V, P, E, H

(change) H

enthalpy

=(change)U + P (change)V

=(change)H reactants + (change)H products

enthalpy is

heat of reaction

calorimeter

qrxn = -qcal

specific heat

s m (change)T

Hess’s Law

overall sum of reactions equal the same as individual steps

standard enthalpy of formation

(change)H formation


1. one mole of compound (products)
2. constituent elements (reactants make up products)
3. standard staes

(change)H formation formulas

= (change) Hrxn + (change) Hvap

= (change) H products - reactants

spontaneous reactions are

endo and exo reactions

entropy (change)S

\-total energy stay constant but distribution changes

\-spontaniety

high temp, (change)S

increases

low temp, (change)S

decreases

solid to liquid to gas

increase in entropy, positive (change)S

increase in entropy means…..sponteneity

increase (molecules are more scattered)

liquid to gas

decrease in entropy means….. sponteniety

decrease (molecules are brought closer together)

gas to liquid

does liquid to gas have a higher entropy then solid to liquid?

yes, the molecules are most scattered in the gaseous state, therefore more spontaneous

second law of thermodynamics

\-entropy in universe increased in spontaneity, (change)Ssys + Ssurr greater than 0

\-Gibbs free energy

(change) S formula

= (change) S products + reactants

third law of thermodynamics

\-entropy of pure, perfect crystal can be take to zero at 0K

(-) G

spontaneous, inc in temp, inc efficiency

(+) G

nonspontaneous, dec in temp, dec efficiency

\

(change) G formula

(change)G products - reactants

coupled reactions

\-when change in G is positive, couple with an negative so they balance out

\-makes efficient and profitable

\-less energy to produce

Gibbs free energy

conversion of energy in order to be most efficient

electromagnetic waves

\-movement of electric charges

\-wavelength, frequency, amplitude

\-can move thru any medium

short wavelength

highest frequency

highest energy

ejects electrons

(gamma, x-rays, UV, visible lights)

long wavelength

lowest frequency

lowest energy

cannot eject electrons

(infrared, microwaves)

wavelengths have different speeds

false: they all have the same speed

max planck

\-atoms could absorb or emit electromagnetic energy in discrete amounts

\-energy is discontinuous

quantum

\-smallest amount of energy

\-when energy is absorbed and increased but goes back to ground state, it goes back as quantum increments

photoelectric effect

amount of frequency determines if electrons will be ejected

will electrons be ejected at a low frequency?

no, because there is no flow with a long wavelength so it is hard to eject

will electrons be ejected at a high frequency?

yes, there is a flow with a shorter wavelength, so it will eject electrons

Bohr’s hydrogen atom

E(n) = -B/n^2

\-energy is zero if electron located infinitely away from nucleus

excitation

\-absorbance

\-atom absorbs energy and jumps to the next level

\-the higher the energy, the less stable

\-the lower the energy, the more stable

emission

\-atom gives off energy, drops to lower level

\-electron prefers to stay at ground state so release energy absorbed

Bohr model: if electron goes down in longer distance, the wavelength is

shorter

Bohr model: if electron goes down in shorter distance, the wavelength is

longer

bohr model: if the wavelengths are all equal, which is greatest

the one closest to the nucleus

change in energy level

(change) E = B \[ 1/ni^2 - 1/nf^2 \]

wavelength of energy level

1/wavelength = R \[ 1/ni^2 - 1/nf^2 \]

electrons moving fast have…wavelengths/frequencies

small, high

electrons moving slow have…wavelengths/frequencies

large, low

quantum number (n)

\-shell

\-size of orbital

quantum number (l)

\-shape of orbital

s:0

p:1

d:2

f:3

quantum number (ml)

\-l to +l

orientation

quantum number (ms)

spin of electron

\-1/2 or +1/2

1s orbital

\-spherical symmetry

n=1, l=0, ml=0

\-electrons spend most time near nucleus

\-highest electron density to nucleus

\-never becomes zero, just decreases as gets far from nucleus

2s orbital

\-2 spherical regions of high electron probability

\-node appears here

node

separation of levels

n-1

angular nodes

l

radial nodes

number of nodes - number of angular noes

pauli exclusion principle

\-no 2 electrons have same energy or quantum numbers

\-lines must go opposite ways

aufbau principle

\-fill orbitals with lowest energy first (ground state)

Hund’s rule

\-fill all first before doubling

\-if not, will increase repulsion and decrease stability

paramagnetism

\-unpaired

\-stronger bc attracted to magnetic field

\-gain mass

diamagnetism

\-all paired

\-weakly repelled to magnetic

\-lower mass

atomic radius

\-half distance between nuclei d/2

\-period trend

* dec left to right- nuclear charge increases
* inc top to bottom- inc in number of e shells

zeff

atomic # - # of e in inner orbital

Z - S

higher nuclear charge means

greater attrition to nucleus, so smaller radius

cations

\-smaller than parent atoms

\-decrease in repulsion as you take e

\-less e = greater attraction = smaller radius

anions

\-bigger than parent atoms

\-inc in repulsion as you add e

\-more e = decrease attraction = bigger radius

ionization energy

\-amount of energy required to remove e

electron affinity

\-potential energy change to e (gaseous state)

\-increase left to right, bottom to top

\-when e is added, energy is release (exothermic)

more protons is… radius

smaller

vigorous reaction

highest electronegative and lowest ionization