Chem Quiz #1 Flashcards
Define element
a type of matter composed of atoms w/ the same atomic # (substance can only correspond to 1 element on periodic table)
Allotrope
Diff. STRUCTURAL forms of the same element in the same phase
- diff. forms can have diff. reactivity
Examples of allotropes
Carbon: Diamond, graphite, & fullerenes
Oxygen: dioxygen (O2) & Ozone (O3)
Sulfur: orthorhombic, monoclinic, amorphous (30 others)
Phosphorus: red, white, & black
Photocatalytic water splitting
Uses sunlight to split H20, butt electrolysis energy doesn’t compensate for energy spent
Compound
substance that contains 2 or more elements
Binary compound
Contains 2 elements
Binary compound examples
H20, H202, CO, & CO2
Ternary compound
Contains 3 elements
Ternary compound examples
C2H5OH (ethanol)
Quaternary compound
Contains 4 elements
Polymorphs
Diff. structural forms of the same COMPOUND in the same phase
Polymorph examples
TiO2 (Anatase & Kutile)
Organic compound made w/
Carbon, Hydrogen, Oxygen, & sometimes Nitrogen
Prussian Blue
absorbs thallium & is treatment for radioactive exposure
Fe4[Fe(CN)6]3
Mixtures
Combination of 2 or more elements/compounds
Example of a mixture
Salt Water (NaCl + H20), Brass (Cu + Zn)
Heterogeneous
Can be physically separated (not uniform)
Heterogenous ex.
solid mixture of blue Cu(NO3)2 x 6H20 & yellow Cds
or
Cereal
Homogeneous
mixed @ molecular level butt NOT chemically bonded
- properties don’t vary through the sample
- can be separated butt not easily
Homogeneous ex.
NaCl + Water or air
Pure Substance
only an element or compound
Material
sample of unknown composition & may be a pure substance/mixture
Greek root of atom
atom (not) tomos (cut)
1st evidence for existence of atoms
analyzing weights of products & reactants
Law of Conservation of Mass
Mass is neither created nor destroyed in a chemical reaction
Law of Definite Proportions
In a pure compound, the constituent elements are always present in a set proportion or % by mass
Law of Constant Composition
All samples of a given chemical compound have the same elemental composition
- H20 is always 11.1% H & 88.9% no matter the source or method or prep
- lead sulfite is always lead sulfite…adding more just leaves leftover unreacted material
Dalton’s 5 Theories of Matter
- Elements consist of tiny indivisible particles called atoms (divisible by ionization
- All atoms of a given element are identical in mass & other properties
- Diff. elements have diff. atom kinds which have diff. masses
- Compounds are formed when atoms of unlike elements combine in small whole # ratios
- Atoms retain their identities in a chemical process & a chem. reaction just changes the atoms bonding
How are atoms divisible
Ionization & nuclear reactions
Law of Multiple Proportions
When 2 elements form a series of compounds, the masses of 1 element that combine w/ a fixed mass of the other element are in the ratio of small integers to each other
Law of Combining Gas Volumes
When gases (@ same pressure & temp.) react, they do so in a definite integer ration by volume. Volume of either reacting gas is the ratio of simple integers
Avogadro’s Hypothesis
Equal volumes of diff. gases @ same temp. & pressure contain equal # of particles. THe distances between the particles are very large, compared w/ the size of the particles
Avogadro’s Hypothesis ex.
1 L of hydrogen gas has the same # of particles as 1 L of oxygen gas or 1 : of nitrogen gas or 1 L of hydrogen chloride
Explain Avogadro vs Dalton beliefs
Dalton: believed particles of an elemental gas consisted of atoms
Avo: believed of an element gas could be atoms, diatomic, or polyatomic & could explain law of combining volumes
Cannizzaro findings
Calculated molecular mass of gaseous compounds & obtained a self-consistent set of relative atomic & molecular masses (accepted that these are diatomic molecules)
ex. if H2 is assigned a mass of 2, O2 is assigned a mass of 32 w/ a 16:1 Oxygen to Hydrogen ratio
Cannizzaro beliefs
- Molecules contain whole #’s of atoms
- Avogadro’s hypothesis is correct & equal volumes of gases under the same condition contain the same # of molecules (masses of equal volumes of gasses are proportional to the relative masses of the particles (atoms/molecules)
Relative molecular mass using Avo.’s hypothesis ex.
ratio of masses of equal volumes of oxygen & hydrogen is 16:1
Cannizzaro accepted
How to determine relative molecular masses of elements that aren’t gasses
study gaseous compounds of those elements
Physical structure of atoms
composed of + charged nucleus (protons & neutrons) and - electrons
facts abt protons
charge of P+ & e- are exactly the same
proton mass = neutron mass
proton mass = 1836 x electron
Evidence for electrons
Cathode/Beta rays
Cathode/Beta Rays
stream of electrons that could be deflected by magnetic & electric fields
OG name for electrons
corpuscles
charge to mass ratio of an electron
e/Me = -1.76x10^8 C/g
Millikan’s Oil Drop Project
observed (-) charged oil drops could be kept from falling by charging electric plates and using an instrument that measures the charge of the drop
e- charge
1.59x10^-19 C
e- mass
Me = 9.11 x 10^-31 kg
Plum Pudding Model
thot (+) charge spread thru entire atom & expected heavy alpha particles would pass through the thin gold foil
Plum Pudding Debunked!?
Most alpha particles passed straight through, but some deflected at a large angle…rutherford concluded most of the mass was concentrated in a very small & dense (+) charged particles
Rutherford Model
nucleus posses net charge of +Ze, w/ Z electrons surrounding the nucleus
Particles w/ thier mass & charge
e-
p+
N
Charge & Mass:
e- = (1-) = 9.11 x 10^-31 kg
p+ = (1+) = 1.67 x 10^-27 kg
N = (None) = 1.67x10-27 kg
Atom structure
tiny nucleus surrounded by electron cloud (without neutrons, protons wouldn’t stick together)
baseball size nucleus = _____ diameter
pea size nucleus weighs _______ tons
4 km
250 million tons
Harold Clayton Ureg discovery, where, & how?
deutrium & won noble prize for it, found in HAVEMEYER, 5L liquid hydrogen distilled to 1mL using distillation apparatus (went from 1st to 2nd floor) then let evaporated liquid condense at room temp. then measured spectrum of light emitted by passing a high xxx
- also lead isotope separation studies
Nuclide characterized by
p+ (Z) or atomic #
# neutrons (N)
mass # (Z + N = A) or (# prontons + # neutrons)
Isotopes
Nuclides of same elements w/ diff. mass #’s (A)
- also means “same place”
- introduced by F. Soddy to explain observations on radioactivity
Isotopes of Hydrogen
protium: 1 p+ & 0 neutrons (99.985%)
deuterium: 1 p+ & 1 neutron (0.015%)
tritium: 1 p+ & 2 neutrons (radioactive w/ 1/2 life of 12.3 years)