Chem Chapter 5,6,7,8

The Ideal Gas Equation in Reaction Stoichiometry

mol B / mol A

Kinetic Molecular Theory Molecular Speeds (root-mean-square speed)

u_rms= √3RT/M

*higher mass=slower

*smaller mass=faster

Diffusion

is the process by which one substance mixes with one or more other substances as a result of the translational motion of molecules

mean free path

Effusion

is the process in which a gas escapes from its container through a tiny hole, or orifice, into a vacuum

rate ₁/ rate₂ = √M₂ / M₁

Real Gas

1. Intermolecular forces of attraction cause the measured pressure of a real gas to be LESS than expected

2. When molecules are close together, the volume of the molecules themselves becomes a significant fraction of the total volume of a gas

Francis Bacon (1620)

idea that heat results from motion

cold might prevent the decay of meat

Count Rumford (1798)

bored cannons

heat is the physical equivalent of work

Thermochemistry

is the study of energy changes that occur during chemical reactions

System

the part of the universe being studied

Surroundings

the rest of the universe

Universe

the system and the surrounding combined

Potential energy

is energy of position or composition

kinetic energy

is the energy of motion

Heat (q)

is the energy that is exchanged between a system and its surroundings due to a difference in temperature

heat is an energy transfer

Thermal equilibrium

occurs when the system and surroundings reach the same temperature and heat transfer stops

internal energy (U)

is the sum of the system’s kinetic energy and potential energy

Chemical energy is stored in the bonds

both position and motion

Exothermic reaction

is a chemical reaction that releases energy as heat to the surroundings

system gets warmer

Endothermic reaction

is a chemical reaction that absorbs energy as heat from the surroundings

system gets colder

Activation energy

is the energy required for the reaction to occur

System does work or work is done to the system

work (w) = force (F) x distance (d)

-work (by the system)

+work (to the system)

PV work =

constant pressure x change in volume

The state of a system

its exact condition at a fixed instant

A state function

is a property that has a unique value that depends only the present state of a system, and does not depend on how the state was reached

The First Law of Thermodynamics

energy cannot be created or destroyed

delta U=

U final - U initial

what is the cause for a change in energy?

heat and work

delta U= heat (q) + work (w)

Heat capacity (C) =

q= C x delta T

q= heat in calories or joules

C= has the units of cal/*C or J/*C

delta T= final T - initial T in *C

Specific heat capacity or Specific heat ( c ) =

q= m x c x delta T

q= heat in calories or joules

m= mass in grams

c= units of cal/g x C or J/g *C

delta T = final T - initial T

Molar heat capacity

is the quantity of energy that must be transferred in increase the temperature of one mole of a substance by 1 *C

Relationships

mass and c are always positive

if q is + then delta T is +

if q is - then delta T is -

Calorimetry

is a device used to make this measurement

measure heat flow

“bomb” calorimeter

used to find heat of combustion

Rearrange of constant pressure

Delta H = q = delta U + P delta V

Standard enthalpy change, delta H

the change in enthalpy for a process in which the initial and final substances are in their standard states

Standard state

is the stable and pure form of a substance at standard pressure and ordinary temperature

1atm for solid, liquid, gas 1M for solutions

Thermochemical equation

a combination of a chemical equation and the corresponding change in standard enthalpy

Negative values

indicate exothermic reactions

Positive values

indicate endothermic reactions

What is the one things you change when reversing a reaction

sign

Hess’s Law

the standard enthalpy of an overall reaction is the sum of the standard enthalpies of the individual reactions into which a reaction may be divided

Standard enthalpy of formation

the change in enthalpy for the formation of one mole of a compound from its elements with all elements in their reference states

Delta H = n products x delta H products = n reactants x delta H reactants

Electromagnetic Radiation

radiant energy

travels through space at he speed of light as oscillating waves where the speed of light =c=2.998 ×10⁸ m/sec

Wavelength

the distance between two corresponding points on a wave

Frequency (v)

a measure of the number of wave cycles that move through a point in space in 1 sec

Speed

a wave is the distance it moves per unit time

c=

wavelength x frequency

Amplitude

the height of the crest: related to the intensity or the brightness

higher: brighter lower: dimmer

Gamma rays = y rays

emitted by nuclear reactions

have the shortest wavelengths and the highest frequencies

Ultraviolet radiation = UV three sub types

UV-C: has the short UV wavelengths and are filtered out by our atmosphere

UV-B: has middle UV wavelengths (sunburns)

UV-A: has ling UV wavelengths and is called “near UV”

Visible light

covers only a small fraction of the entire electromagnetic spectrum

Visible spectrum

400-750nm

Violet light

short wavelengths and high frequency

Red light

long wavelengths and low frequency

Infrared Radiation (IR)

is associated with radiant heat

Microwave and radar

have the appropriate energy to cause molecules to rotate

Radio waves

are use for communication, including FM and AM

Long radio waves

have the longest wavelengths and the lowest frequencies

Refraction

the wave strikes a boundary and it changes speed and direction

Dispersion

light is separated spatially into all of its components

White light

is composed of different colors that can be separated by a prism

sources: sun, light bulbs

Constructive interference

is in phase, adds amplitude and is brighter

Destructive interference

is out of phase, cancels amplitude and forms a darker region

Spectrum

is a plot of the intensity of light as a function of the wavelength or frequency of the light

Continuous spectrum

contains all the wavelength of light in the visible spectrum

produced by white light

Line spectrum

contains a pattern of distinct colored lines, each representing a single wavelength if light

produced by an element that has been heated or given an electric charge

each element has a distinct line spectra which is also called the atomic fingerprint

Planck’s Quantum Theory

light is emitted in discrete or definite packets called quanta

quantum is a minimum quantity of energy that can be emitted at any given time from a hot object

Duality of light

light exists as both waves and particles (photons)

Characteristics of waves

frequency and wavelength

c=w x f

characteristic of photons

E_photon = hv

1 Einstein =

1 mol of light

What did Bohr suggest?

electron of atoms exist in specific energy level, electrons cannot have just any amount of energy, but must have certain specified values

What did de Broglie present?

if light can exhibit characteristics of both waves and particles, then prehaps particles of matter can also have wave characteristics

What did Heisenberg conclude?

Created the uncertainty principal

it is impossible to determine precisely both the position and the energy of an electron

the specific path a=of an electron cannot be determined

What did Schrodinger develop?

Mathematical equations that solve wave functions by finding the probability of the electron in a specific region

these areas are represented by orbitals

Orbitals

three dimensional regions in space where electrons are likely to be found, not a circular pathway

lower energy: smaller orbitals higher energy: larger orbitals

What are the 4 most common orbital types

s: sharp

p: principal

d: diffuse

f: fundamental

l

is the angular momentum quantum number, give the shape of the orbital

m₁

is the magnetic quantum number, represents the direction and number of orbitals in subshell

s orbital

l=0 m₁= 0

each orbital can contain TWO electron

p orbitals

l=1 m₁= -1,0,1

there are three orbitals, and each orbital can contain two electrons for a total of 6 electrons in the prbitals

d orbitals

l=2 m₁= -2,-2,0,1,2

there are FIVE orbitals and each orbital can contain two electron for a total of 10 electrons in the orbital

f orbitals

l=3 m₁= -3,-2,-1,0,1,2

there are SEVEN orbitals, each orbital can contain two electrons for a total of 14 electrons in the orbital

m₂

+1/2 and -1/2

Electrons spinning in opposite directions producing different energies based on orientation

Pauli exclusion principle

Theory that at most two electrons can be assigned to the same orbital in the same atom, and these two electrons must have opposite spins

Different spins - paired

Parallel spins - must be different orbitals

Penetration and Shielding

The closer electrons shield positive charges from the nucleus from affecting the electrons in orbitals farther from the nucleus

Order of electron configuration

1s→2s→2p→3s→3p→4s→3d→4p→5s→4d→5p→6s….

Hund’s Rule

The most stable arrangement of electrons in the same subshell is to have the maximum number of unpaired electrons - all with the same spin

Distribution rule in orbitals that hold more than two electrons

Inner (core) electrons

are those an atom has in common with the previous noble gas and any completer transition series (d or f)

Outer electrons

are those in the highest energy (highest n value)

farthest from the nucleus

Valence electrons

are those involved in forming compounds

Main group

valence electrons = outer electrons

Transition elements

valence= outer plus unfilled d electrons

Electron Configuration for Cations

• positively charged ions

• subtract the number of the charge from the total number of electrons

• move to the left the number of spaces equal to the charge on the periodic table

Electron Configuration for Anions

• Negatively charges ion

• Add the number of the charge to the total number of electrons

• move to the right the number of spaces equal to the charge on the periodic table

Atomic Size

described in terms of atomic radius

Atomic radius increases

from top to bottom

Atomic radius decreases

form left to right

Ionization energy

a measure of the energy required to remove a valence electron from a gaseous atom to form a gaseous ion

Successive Ionization Energies

IE₃ > IE₂ > IE₁