Colomac Semester One AP CHEM finals

two fundamental concepts of chemistry
1. matter is composed of various types of atoms
2. one substance changes to another by reorganizing the way atoms are attached to each other
natural law vs. theory
– natural law = summary of observed (measurable) behavior
– theory = attempt to explain behavior (why it happens)
fundamental SI units: mass, length, time, temperature, amount of substance, volume, electric current, luminous intensity
kilogram (kg), meter (m), second (s), Kelvin (k), mole (mol), liter (L), ampere (A), candela (cd)
mass vs. weight
– mass = measure of the resistance of an object to a change in its state of motion
– weight = force that gravity exerts on an object
homogeneous vs. heterogeneous
– homogeneous = visibly INDISTINGUISHABLE parts –> solution
– heterogeneous = visibly DISTINGUISHABLE parts –> pure substance(constant composition) or 2+ solutions
methods to seperate components into mixtures
1. distillation
2. filtration
3. chromatography = stationary phase (solid), mobile phase (liquid or gas)
4. paper chromatography = stationary phase is paper
percent uncertainty
if given A±B(uncertainty),
percentage uncertainty = (B/A) x 100
calculating uncertainty
1. adding/subtracting
2. mutiplication/division
3. to a power
1. absolute uncertainties can be added
2. convert absolute uncertainty to percent uncertainties, then add
3. percent uncertainty times the power
What to do with sigfigs when ADDING percent uncertainties during multiplication/division of absolute uncertainties?
if added percent uncertainties are:
– greater than or equal to 2%, 1 sigfig
– less than 2%, no more than 2 sigfigs
percent error
[(|actual – theoretical|) ? theoretical] x 100
if % uncertainty > % error
– random errors
– instrument’s fault
– more trials will help improve data
if % uncertainty < % error
– systematic errors
– your fault
Law of Conservation of Mass
– mass is neither created nor destroyed
– experiments showed combustion involved oxygen, not phlogiston
– Priestly, Lavoiser
Law of Definite Proportion
– a given compound always contains exactly the same proportion of elements by mass
– constant composition of compounds
– Proust
Law of Multiple Proportions
– molecular formula can be reduced to emperical formula
Greeks questioned whether matter was:
1. continuous/infinitely divisible
2. composed of small, indivisible parts (Democritus of Abdera, Leucippos = coined the term atom)
Greg Bauer/Paracelsus
laid foundations of chemistry
first chemist to perform truly quantitative experiments
Dalton’s Atomic Theory
1. each element is made up of tiny particles called atoms
2. the atoms of a given element are identical; the atoms of different elements are different in fundamental ways
3. chemical compounds formed when different elements combine
4. atoms themselves arent changed in chemical reaction, but reorganized
same number of protons, different number of neutrons
if all atoms are composed of these same components, why do different atoms have different chemical properties?
number and arrangement of electrons, therefore 3 of electrons possessed by given atom greatly affects its ability to interact with other atoms
properties of atom: mass, # of protons, # of neutrons, # of electrons,
protons + neutrons, atomic #, mass – protons unless its an isotope, # of protons unless it has a charge
chemical vs covalent vs ionic BONDS
– forces that hold atoms together, in general
– share electrons… form molecules
– transfer electrons… opposites attract
radio isotope
isotope that contains an unstable nucleus
element will decay if…
number of neutrons are too high or too low
all atoms over __ protons are radioactive
alpha particles
– positively charged
– ionizing radiation: strips electrons off things they pass through
– can’t pass through paper or large clothing
*4,2,He on right side
beta particles
– negatively charged
– neutron decays to a proton and electron (N –> P+ + e-
– smaller than alpha, therefore better at ionizing than alpha
– cant pass through 3 mm aluminum foil
*0,-1,e on right side
gamma rays
– no charge
– not made of matter, PURE ENERGY = LOTS OF ENERGY, form of electromagnetic energy
– usually emitted after transmutation (nucleus changed)
– can’t pass through 60 cm Al or 7 cm Pb
*0,0,Y on right side
electron capture
– no charge
– proton is turned into neutron (P+ e- –> N)
– one of the inner-orbital electrons is captured by the nucleus
– *0,-1,e on left side
positron emission (B+)
– positive charge
– instead of 0,-1,e it is 0,+1,e
– antimatter, destroyed when they encounter an electron
– electron + positron = 2 gamma rays
*0,+1,e on right side
collision caused a change in nucleus, the problems you solve the math to figure out blank elements and yadayada
– occurs in nuclear decay, fusion, and fission
splitting a nucleus into 2 or more elements, some mass lost, breaks law of conservation of matter, chain reaction, e=mc^2
when 2 nuclei combine, lots of energy can be released, occurs in stars
Geiger Counter
used to detect radioactive activity by measuring current that radiation produces in argon gas
Ammonium, Carbonate, Chlorate, Chromate, Hydrogen Carbonate (bi), Hydroxide, Nitrate, Permanganate, Phosphate, Sulfate
NH4+, CO32-, ClO3-, CrO42-, HCO3-, OH-, NO3-, MnO4-, PO43-, SO42-
Relative Atomic Mass (Ar)
mass of a single atom relative to C-12….isotope

isotope mass / mass of carbon (which is 12) = Ar

Relative Molecular Mass (Mr)
sume of the Ar in a molecule
percent composition
% mass of element = (mass of element/mass of compound) x 100
molecular vs empirical
real amount and reduced
limiting reactant
runs out first, SMALLER
percent yield
(actual yield/theoretical yield) x 100
percent to mass mass to mole divide by small multiply till whole…. method used when?
determining molecular/emperical formulas
grams to moles to moles to grams……method used when?
stoichiometric caculations of limiting/excess reactants and products
mass spectrometer
instrument used to determine the masses of atoms and their isotopic composition by the deflection of ions in a magnetic field

vaporization, ionization, acceleration, deflection, detection

to find excess reactant
1. start with limiting ~ COMPARED TO ~ excess
theoretical yield
maximum amount of a product formed when limiting reactant is completely used up
to determine theoretical yield of a product
start with limiting reactant ~ COMPARED TO ~ product calculating theoretical yield for
polar molecule
unequal charge distribution
+ ends of water molecules attract to anions of ionic solid, and – ends of water molecules attract to cations of ionic solid
when ionic substances (salts) dissolve in water, they break up into _______
INDIVIDUAL cations and anions
when an ionic solid dissolves in water, ions become:
1. hydrated
2. dispersed
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