chapters 5 and 6

energy

the ability to do work or transfer heat

thermodynamics

study of energy and its transformation

thermochemistry

study of chemical reactions and the energy change that involve heat

like chargers closer to Eel>0

smaller separation, greater repulsion and higher Eel

like charges closer to Eel=0

greater separation, less repulsion and lower Eel

Opposite charges closer to Eel<0

smaller separation, greater attraction, lower Eel

Opposite charges closer to Eel=0

greater separation, less attraction, higher Eel

attraction between ions

attraction is seen between oppositely charged ions

when energy is released

chemical bonds are formed <0

when energy is absorbed

when chemical bonds are broken >0

First law of thermochem

energy cannot be created nor destroyed it can only be transferred. sunlight is converted to chemical energy in green plants

system

what we single out to study, a chemical reaction represents a system

surroundings

are everything else that surrounds the system

Open system

can exchange heat and mass with its surroundings

closed system

can only exchange heat and mass with its surroundings

isolated system

cannot exchange heat nor mass with its surroundings

Internal energy

the change in internal energy of a system is the sum of the heat added to the system and the work done on the system.

delta E is a state function

meaning that it only depends on the initial and final states, it does not depend on path

a positive delta E

when the system gains energy from the surroundings

a negative delta E

when the system loses energy to the surroundings

Internal Energy of a system

is the sum of all kinetic energy and potential energies of all components of the system

endothermic

when heat is absorbed by the system from the surroundings, there is a temp drop

exothermic

when heat is released by the system into the surroundings, there is a temp increase

positive q

heat in to the system

negative q

means heat out of the system

positive w

means work done on system

negative w

work done by the system

delta E +

means net gain of energy system

negative delta E

means net loss of energy in the system.

Pressure-Volume Work

work being done by the gas in a reaction done in a vessel that has been fitted with a piston w=-PV, work is negative because it is work done by the system

Enthalpy

if a process takes place at a constant pressure and the only work done is this pressure-volume work, we can account for heat flow during the pressure

Enthalpy is defined as the

the interval energy plus the product of pressure and volume H=E+PV

change in enthalpy 

products - reactants

enthalpy of reaction

the change in enthalpy during a chemical reaction, indicating the heat absorbed or released.

Enthalpy guidelines 1

enthalpy is an extensive property, so it depends on the amount

enthalpy guidelines 2

the enthalpy change is the same regardless of the pathway taken between reactants and products.

enthalpy guidelines 3

the enthalpy of a system depends on its state, not how it got there.

calorimetry

the measurement of heat flow, the tool to measure is called a calorimeter

heat capacity

the amount of energy required to raise the temperature of a substance

specific heat

if the amount of the substance heated is one gram

molar heat

if the amount is one mole

Bomb calorimetry

constant volume, the heat absorbed or released by the water is a very good approximation of enthalpy change for the reaction

Hess’s Law

if a reaction is carried out in a series of steps, delta H for the overall reaction equals the sum of the enthalpy changes for the individual steps

bond enthalpies

we can predict whether a chemical reaction will be endo or exo thermic using the energies

what do you do for bond enthalpy

add bond energy values for all bonds broken (+), subtract bond energy values for all bonds formed (-)

electron configuration

the way electrons are distributed

what is the most stable organization

in the lowest possible energy called the ground state

electron configuration and energy

orbitals fill in increasing order of energy, different areas correspond to different types of orbitals, s and p are main group elements

valence electrons

elements in the same group of the periodic table that have the same number of electrons in the outermost shell

core elements

the filled inner shell electrons, they are noble gases and always included filled sublevels

transition metals and configuration

follow by filling the s then d and f before p

Chromium, Mo

it is allowed to have 4s^1 and then add another to d as it is an anomaly

hunds rule

states that electrons will fill degenerate orbitals singly before pairing up in the same orbital.

s orbital

the value of l for s is 0, they are spherical in shape, the radius of the sphere increases with the value of n

s orbital and peaks

for an ns orbital, the number of peaks is n. the number of nodes is n-1

nodes or n

where there is zero probability of finding an electron, as n increases the electron density is more spread out and there is a greater probability of finding an electron from the nucleus

p orbital

the value of l is 1, they have two lobes with a node between them

d orbital

the value of l is 2, they have a more complex shape and can contain up to 10 electrons. most have four lobes but one looks like a pacifier 

f orbital

very complex shapes, seven equivalent orbitals in a sublevel, l=3

hydrogen atom orbital energies

one electron hydrogen atom, orbitals on the same energy level have the same energy. Also called as degenerate orbitals

Many electron atoms

as the number inc, so does the repulsion, in atoms with more than one electron, not all orbitals on the same energy levelare degenerate due to electron-electron interactions that create energy level splitting.

electromagnetic wave

moves as waves through spaces at the speed of light

wavelength

the distance between corresponding points on adjacent waves 

frequency

the number of waves passing a given point per unit of time is the frequency 

for waves traveling at the same velocity

the longer the wavelength the smaller the frequency

frequency and energy are

related such that higher frequency waves carry more energy.

black body radiation

an object glows when heated, the wave nature of light does not explain how an object can glow when temp increases

quanta

singular quantum

photoelectric effect

the phenomenon where light causes the emission of electrons from a material, each metal has a different energy at which it ejects electrons, at lower energy, electrons are not emitted

continuous spectrum

a spectrum that shows all wavelengths of light without any gaps. It results from the emission or absorption of light by a hot object or gas.

line spectrum

a spectrum showing distinct lines corresponding to specific wavelengths of light emitted or absorbed by a substance, characteristic of different elements.

the bohr model 1

only orbitals of certain radii correspond to specific energies are permitted for electron in a hydrogen atom

the bohr model 2

an electron in a permitted orbit is in an allowed state of energy, will not radiate energy ad will not spiral into the nucleus

bohr model 3

energy is emitted or absorbed by the electron only as the electron changes from one energy state to another.

ground state

electrons in the lowest energy state n=1

excited state

energy higher n>1

photon absorbed

a positive delta E energy is absorbed, when it goes from big number to small

photon emitted

a negative delta E energy meaning it is released, when it goes from a smaller number to big number

limits of bohr model

only works for hydrogen, electrons have wavelike properties that must be accommodated

important ideas of bohr

electrons exist only in certain discrete energy levels, which are described by quantum numbers, energy is involved in transition of an electron from one level to another

the wave behavior of matter

if light can have material properties, matter should exhibit wave properties, wavelength= h/mv

double slit experiments(light) one opening

when light passes through a small opening, its wave nature causes it to be diffracted

double slit experiments(light) two openings

when light passes through two small openings, the diffraction patterns interfere and create an interference pattern

double slit electrons

when electrons interact with the double slit experiment, we see an interference pattern showing the wave nature of electrons

the uncertainty principle

the dual nature of matter placed a limitation on how precisely we can know both momentum and position, the more precise the momentum of a particle, the less precisely its position is known

quantum mechanics

both the wave and particle nature of matter could be incorporated, deals with dot density and probability of finding electron in the region

wave function

a mathematical description of the quantum state of a system, representing the probability amplitude of a particle's position and momentum.

electron density

the square of the wave function, or probability of where and electron is likely to be found in a given region of space.

quantum numbers

values that describe the energy, shape, and orientation of an electron's orbital in an atom, including principal, angular, and magnetic quantum numbers.

quantum number n

the energy level n which orbital resides, positive integer values, as increases the orbitals become larger and the electron spends more time further away from the nucleus also has a high energy and less tightly bound

quantum number l

defines the shape of the orbital, allowed values of l are integers ranging from 0 to n-1, s=0, p=1,d=2,f=3

quantum number m

describes the three-dimensional orientation of the orbital. can be get but follows a specific pattern

spin quantum numbers ms

indicate the intrinsic angular momentum of an electron, with possible values of +1/2 or -1/2, determining the direction of the electron's spin.

pauli exclusion principle

no two electrons in the same atom can ahve same spinor quantum numbers, ensuring that each electron in an atom is unique.

when asks for thermal energy being released or absorbed

start with what the give and use it for stoich but at the end put kj on the top