General Chemistry Flashcards
Atomic Mass vs Atomic Weight
Weight of a proton/neutron
Isotope abundance
Atomic mass- mass of single atom
Atomic weight - mass of one mole of an element
Weight of a proton/neutron = 1.66x10^24 g
More stable isotopes are found in greater abundance in nature (and have longer half lives)
Rutherford model
Bohr model
Rutherford model - atom mostly empty space; positively charged center with negative elective orbiting randomly
Bohr model - electrons travel in fixed orbits at set distances (orbitals); energy level increases farther away from nucleus; quanta of energy radiated off an atom is equal to difference b/w 2 adjacent orbitals
L= nh E= -R(H)
2 pi n^2
R(H) = rydbergs constant = 2.18x10^-18J/electron
Planck
planck’s constant
Emission & Absorption
Planck - first quantum theory - atoms radiated energy in small discrete bundles called quanta
E=hf where h = 6.6x10^-34 J•s
J =
Emission & absorption
E= hc = -R(H)((1/ni^2)-(1/nf^2))
Lambda
Nonpolar covalent bond
When atoms have identical or nearly identical electronegativities and so share electron pairs with equal distribution of electrons
Ionic Bonds
High melting point
High boiling point
Dissolve readily in water and other polar solvents
In aquesous state, are GOOD conductors of electricity
Form crystalline lattice in solid state - more attractive forces
Covalent bonds
Low melting and boiling points
Don’t break down into ions –> POOR conductors of electricity
properties - Bond length, bond energy, polarity
Polar covalent bonds
difference in electronegativities (0.5 - 1.7) causes separation of charge across the bond - but not enough to form ionic bond
has partial negative and partial positive charges and dipole moment (p=qd) p is in Coloumb-meters
Coordinate Covalent bond
both of the shared electrons originate on the same atom
-meaning lone pair of one atom attacked another atom with unhybridized p-orbital to form a bond
Lewis Acid
Lewis Base
Formal charge
Lewis Acid - accepts lone pair of electrons
Lewis Base - donates pair of electrons
Formal charge = V = N(nonbonding electrons) - (0.5*N(bonding electrons))
Formal charge vs oxidation state
Formal charge underestimates effect of electronegativity and oxidation state overestimates effect of electronegativity
Gram equivalent weight
Gram equivalent weight = molar mass/n
where n is number of particles of interest produced or consumed per molecule of the compound in the reaction
equivalents = mass of compound/gram equivalent weight
Normality (N)
normality = equivalents/L
in 2 N solution of H2CO3, the molarity of H2CO3 is ).5 M because H2CO3 has 2 protons/hydrogens
law of constant composition
Empirical vs molecular formula
Percent composition
any pure sample of a given compound will contain the same elements in an identical mass ratio
H2O molecules will always have 2 hydrogen atoms for every one oxygen atom
empirical - simplest whole number ratio of elements
molecular - exact number of atoms of each element
percent composition - of an element (by mass) - is percent of specific compound that is made up of a given element
Combination RX (reaction)
Decomposition RX
Combustion RX
Single -displacement RX
Double - Displacement RX/metathesis
Neutralization RX
Combination RX (reaction) - two or MORE reactants form one product
Decomposition RX - single reactant breaks down into one or more products; usually as a result of heating, high frequency radiation, electrolysis
Combustion RX - involves a FUEL, usually a hydrocarbon, and an OXIDANT(normally oxygen); forms carbon dioxide and water!!!
Single -displacement RX - atom/ion is replaced by an atom or ion of another element
Metathesis RX/double displacement - occurs when one of the products is removed from solution as a precipitate or gas when two of the original species combine to form a weak electrolyte that remains undissociated in solution
Neutralization RX - specific double displacementl acid reacts with base to produce a salt and usually water
Percent yield
percent yield = (actual yield/theoretical yield) *100%
Ionic compounds naming
Pg 135 gen chem
Solid vs aqueous ionic compounds
solid - lattice arrangement so POOR conductors of electricity
in aqueous solution - ion-dipole interactions between ionic components and water molecules exist - so solution of ions can conduct electricity
electrolytes -
solutes that enable solutions to carry currents
~pure water is a poor conductor
` strong electrolytes are ionic compounds with HIGHLY polar covalent bonds that dissociate easily when dissolved (EXAMPLES - NaCl and KI)weak electrolytes - hydrolyzes/ionizes incompletely (EXAMPLES - Hg2I2, acetic acid and other weak acids, ammonia, other weak bases)
NONelectrolytes - dont ionize in water at all - like nonpolar gases and organic compounds (O2, CO2, glucose)
Intermediate
rate-determining step
collision theory of chemical kinetics
activation energy
reaction rate
Intermediate
rate-determining step - slowest step; prevents rest of RX from occurring
collision theory of chemical kinetics - rate of RX is proportional to the number of collisions per second b/w the reacting molecules
activation energy - minimum energy of collision necessary for a RX to take place
reaction rate = Z x f
Z = total number of collisions occurring per second
f = fraction of collisions that are effective
Or use the Arrhenius equation to find reaction rate where k = A* e^(-Ea/RT) where k is rate constant, R is ideal gas constant, R is activation energy, T is temp in kelvins
reaction rate = Molarity/second
rate = k[A]^x * [B]^y
Transition state vs reaction intermediate
Factors that affect reaction rate
transition state - theoretical construct that exist at point of maximum energy
reaction intermediate - distinct molecules with finite lifetimes
factors that affect reaction rate - reaction concentrations, temperature, medium, catalysts (homogenous vs heterogenous catalysis)
Keq for reversible reaction
reaction order vs equilibrium constant expression
for reversible reaction, Keq = k (forward reaction)/ k (of reverse reaction)
notes on Pg 166 Gen chem
zero-order
first order
second order RX
zero-order ``````` rate = k first order `````` rate = k[A] second order RX ```````rate = k[A]^2
what does it mean for enzyme to be saturated?
When there is too much substrate, it will attach to all the enzyme and will saturate the enzyme, thereby reaching the maximal turnover rate of the reaction. basically enzymes can only make the reaction go so fast to a point
