Chem 105a Midterm 2

10/15, content from lectures 11-21/weeks 5-8

calorimetry

experimental procedure used to measure the heat involved in a reaction

relationship between speed of light, wavelength, & frequency

c = λv

relationship between energy of photon, speed of light, & wavelength

E_ph=hc/λ

h

Planck’s Constant

λ

wavelength

v

frequency

c

speed of light

the photoelectric effect

when metals are hit with light they occasionally emit electrons

de Broglie Relationship

wavelength of a particle is inversely proportional to its momentum

light/electromagnetic radiation

form of energy that moves as waves of oscillating electric and magnetic fields

amplitude

height of wave/measure of wave intensity

wavelength (λ)

distance between crests of wave, how long wave takes to reach same vertical point

frequency (v)

number of cycles of a wave that pass through a point in one second

photon

particle of light, behaves as wave

Planck’s constant (h)

6.626 ⋅ 10^-34 J ⋅ s

Heisenberg uncertainty principle

it is impossible to determine both the position and momentum of a particle at the same time

kinetic energy

energy of motion

thermal energy

energy of temperature

potential energy

energy something has due to its position

chemical energy

potential energy in chemical bonds

the system

the area being studied

the surroundings

everything outside of the system which touches the system

the universe

system + surroundings

heat (q)

transfer of thermal energy

work (w)

energy of changes in pressure or volume

specific heat capacity

amount of energy in Joules needed to raise temperature of 1g of substance by 1°C

heat capacity

amount of energy in Joules needed to raise temperature of an amount of substance by 1°C

energy

capacity to do work or supply heat

endothermic process

process in which system absorbs heat from the surroundings

exothermic process

process in which system releases heat to the surroundings

thermodynamics

study of energy transfer in a reaction

internal energy

all energy in a system

calorimetry

experimental procedure used to measure the heat involved in a reaction

change in enthalpy (ΔH)

total heat absorbed/released by a system

enthalpy (H)

heat associated with breaking and forming of bonds in a chemical reaction

standard enthalpy (ΔH°)

enthalpy of a reaction in standard state

standard state of gas

1 atm of pressure

standard state of liquid/solid

most stable form at a specific temperature and 1 atm of pressure

standard state of aqueous solution

1M

standard enthalpy of formation (ΔH_f°)

change in heat when 1 mole of compound is formed from pure elements in standard states

Planck’s Constant

6.626 · 10^-34 J · s

speed of light

3.00 × 10⁸ m/s

orbital

probability distribution map of where an electron may be located

principal quantum number

n

principal quantum number (n)

distance from the nucleus (higher n = further from nucleus)

possible values of n

any positive integer, 1 to infinity

angular momentum quantum number

l

angular momentum quantum number

indicates shape of orbital

possible values of l

from 0 to n-1

magnetic quantum number

m_l

magnetic quantum number

indicates orientation of oribital

possible values of m_l

-l to +l (including 0)

spin quantum number

m_s

spin quantum number

indicates direction of spin of electron

possible values of m_s

±½

de Broglie wavelength

wavelength of a particle

equation for de Broglie wavelength

λ_db=h/mv (velocity not nu)

Pauli exclusion principle

no two electrons in the same atom can have 4 identical quantum numbers

Aufbau principle

electrons will fill lowest available energy level (n) first

Hund’s rule

every orbital of the same energy level (n) will get 1 electron before any get 2 electrons

valence electrons (in main group elements)

electrons in orbital with highest n value

valence electrons (in transition metals)

electrons in orbitals with highest and second highest n values

core electrons

electrons in completely filled orbitals with n less than highest n

first law of thermo

energy is neither created nor destroyed

endothermic

+q

exothermic

-q

standard enthalpy of formation for pure elements in standard state

0kJ

ΔH_rxn

[(coefficent of reactant A *ΔH_f°)+(same thing for other reactants) - [same thing for products]

Hess’s Law

the total enthalpy change (Δ H) of a chemical reaction is the same whether it takes place in a single step or in a series of multiple steps

If a chemical reaction is reversed

ΔH changes sign