Mcat Chemistry

Front 1

What is an atom made up of?

Back 1

nucleus: contains protons and neutrons
electrons: surround nucleus
made up mostly of empty space

Front 2

mass number (A)

Back 2

sum of the number of protons and neutrons

Front 3

Atomic number (Z)

Back 3

number of protons

Front 4

Isotope

Back 4

element that contains a different number of neutrons than the normal element

Front 5

mole

Back 5

1 mole = 6.022 x 10^23 atoms

Front 6

metals

Back 6

large atoms that tend to lose electrons to form cations or position oxidation states, form ionic oxides (left side of periodic table)

Front 7

nonmetals

Back 7

lower melting point than metals , form negative ions, form covalent oxides (right side of periodic table)

Front 8

alkali metals (group 1A)

Back 8

soft solids with low densities and low melting points, easily form cations

Front 9

alkaline earth metals (group 2A)

Back 9

harder, more dense solids that melt at higher temperatures and form 2+ cations. These are generally less reactive

Front 10

Periodic table trends

Back 10

-atomic radius increases from top of periodic table to bottom
-ionization energy increases from left to right and from bottom to top
-electronegativity increases left to right and from bottom to top
-electron affinity increases from left to right and from bottom to top

Front 11

ionization energy

Back 11

energy necessary to detach and electron from a nucleus

Front 12

electronegativity

Back 12

tendency of an atom to attract an electron

Front 13

electron affinity

Back 13

willingness to accept an additional electron

Front 14

covalent bond

Back 14

two electrons are shared between two nuclei

Front 15

bond length

Back 15

point where energy level is lowest

Front 16

bond disassociation energy

Back 16

energy necessary to separate a bond

Front 17

principle quantum number (n)

Back 17

1st quantum number designates shell level. The larger the quantum number, the greater the size and energy of the orbital

Front 18

valence electrons

Back 18

located in the outer most shell and contribute most to an elements chemical properties

Front 19

azimuthal quantum number (l)

Back 19

2nd quantum number designates subshell s,p,d, f.
if l=0, s subshell.
l=n-1

Front 20

magnetic quantum number (m)

Back 20

3rd quantum number designates orbital. each subshell will have orbitals from-l to +l

Front 21

electronic spin quantum number (ms)

Back 21

4th quantum number has value of -1/2 or +1/2 and signifies direction of the electron in the orbital

Front 22

Pauli exclusion prinicple

Back 22

no two electrons can have the same four quantum numbers

Front 23

Aufbau principle

Back 23

-for each new proton added to create a new element, a new electron is added too
-electrons look for orbitals available at the lowest energy state in the subshell with the lowest energy

Front 24

Hund's rule

Back 24

electrons will not fill any orbital in the same subshell until all orbitals in that subshell contain at least 1 electron

Front 25

planck's theory

Back 25

E=hf
h=6.6 x10^-34 Js

when an electron falls from a higher run to a lower rung, energy is released
photons can bump electrons up to the next level

Front 26

standard temperature and pressure (stp)

Back 26

0 degrees Celsius and 1 atm

Front 27

Ideal gas characteristics

Back 27

1. gas molecules have zero volume
2. gas molecules exert no forces other than repulsive forces due to collisions
3. gas molecules make completely elastic collisions
4. the average kinetic energy is directly proportional to the temperature of the gas

Front 28

ideal gas law

Back 28

PV=nRT

P=pressure
V=volume
n=# of moles
R= universal gas constant
T= temperature in Kelvin

Front 29

standard mole volume

Back 29

one mole of any gase behaving ideally should occupy 22.4L

Front 30

partial pressure

Back 30

partial pressure of a= mole fraction of a times the total pressure

Front 31

Dalton's law

Back 31

the total pressure is equal to the sum of all of the partial pressures

Front 32

Grahm's Law

Back 32

average speed is inversely proportional to the square root of its mass

v1/v2=(m1)^1/2/(m2)^1/2

Front 33

effusion

Back 33

spread of gas from high pressure to low pressure

effusion rate is inversely proportional to the square root of the mass

Front 34

diffusion

Back 34

spreading of 1 gas into another gas or empty space

Front 35

kinetics

Back 35

rate of reaction typically as it moves to equilibrium

Front 36

thermodynamics

Back 36

deals with the balance of reactants and products after they have reached equilibrium

Front 37

collision model

Back 37

in order for a chemical reaction to occur, the reacting molecules must collide. most collisions do not result in reactions. to react, molecules much reach activation energy and have the proper spatial orientation
-rate of rxn increases with temp because more collisions with high energy likely to occur

Front 38

rate determining step

Back 38

rate of the slowest elementary step, determines the rate of the overall reaction. Steps after slow step make no conrtibutions to rate law

Front 39

catalyst

Back 39

substance that increases the rate of the reaction without being permanently consumed or altered. Most work by lowering activation energy, which means more collisions have sufficient energy to create a reaction, which increases the overall rate

Front 40

heterogeneous catalyst

Back 40

different phase than reactants and products

Front 41

homogeneous catalyst

Back 41

same phase as reactants and products

Front 42

equilibrium

Back 42

when the forward reaction rate is equal to the reverse reaction rate with no change in concentration of products or reactants

Front 43

Law of Mass action

Back 43

k (equilibrium constant)= products divided by reactants

no solid or pure liquids (eg H2O) in law of mass action

Front 44

reaction quotient (Q)

Back 44

Q=products divided by reactants
-use to predict what direction a reaction will go in
if Q is equal to k, then the rxn is at equilibrium
if Q is greater than K, the products are greater than the reactants and the reaction goes left
if Q is less than K, the reactants are greater than the product and the reaction shifts right

Front 45

Le Chatelier's Prinicple

Back 45

When a system at equilibrium is stressed, the system will shift in the direction that reduces stress

three stressors:
1. addition or removal of product or reactant
2. changing the pressure of the system
3. heating or cooling the system

Front 46

open systems

Back 46

exchange both mass and energy with their surroundings

Front 47

closed systems

Back 47

exchange energy but not mass

Front 48

isolated systems

Back 48

do not exchange energy or mass

Front 49

extensive properties

Back 49

properties are proportional to the size of the system

(eg. volume, number of moles)

Front 50

intensive properties

Back 50

properties that are independent of the size of the system

(eg. pressure and temperature)

Front 51

state functions

Back 51

properties that describe the state of a system, pathway independent

(eg. number of moles, enthalpy)

Front 52

path functions

Back 52

properties that depend on the pathway used to achieve any state

(eg work and heat)`

Front 53

heat

Back 53

natural transfer of energy from a warmer body to a cooler body

Front 54

work

Back 54

any energy transfer without heat

Front 55

Forms of Heat

Back 55

1. Conduction
2. convection
3. Radiation

Front 56

conduction

Back 56

thermal heat transfer of energy via molecular collisions; requires direct physical contact

Front 57

convection

Back 57

thermal energy transfer via fluid movements. Differences in pressure or density drive warm fluids to cooler areas

Front 58

radiation

Back 58

thermal energy transfer through electromagnetic waves

Front 59

work

Back 59

transfer of energy, not heat

w=P deltaV at constant pressure

if the volume remains constant, no PV work is done

Front 60

1st Law of thermodynamics

Back 60

the energy of the system and surroundings is always conserved

E= w +q

Front 61

2nd Law of thermodynamics

Back 61

heat cannot be completely changed to work in a cyclical process

Front 62

internal energy

Back 62

collective energy of molecules measured on a microscopic level, does not include mechanical energy

Front 63

Hess' Law

Back 63

when you add reactions, you can add their enthalpies too

Front 64

zeroth law of thermodynamics

Back 64

two systems at equilibrium with a third system are at equilibrium with each other

Front 65

enthalpy

Back 65

man-made property that accounts for the extra capacity to do PV work

H= U + PV

Front 66

standard enthalpy of formation

Back 66

change in enthalpy for a reaction that creates one mol of that compound from its raw elements in their standard state

Change in enthalpy of reaction = the standard enthalpy of products - the standard enthalpy of the reactants

Front 67

endothermic reaction

Back 67

enthalpy change is positive, produces heat flow into the system

Front 68

exothermic reaction

Back 68

enthalpy change is negative, produces heat flow into the surrounding

Front 69

entropy

Back 69

natures tendency to create the most probable situation that can occur in a system; natures tendency toward disorder

Front 70

2nd law of thermodynamics

Back 70

entropy in an isolated system will never decrease

Front 71

3rd law of thermodynamics

Back 71

assisn by convention a zero entropy value to any pure substance

Front 72

Gibbs free energy

Back 72

change in gibbs free energy is equal to the change in enthalpy minus the change in entropy times temperature

when G=0, at equlibrium
when G is negative, spontaneous