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Chemistry 132 Midterm
Definitions, Equations, Etc
53
Chemistry
Undergraduate 3
10/12/2014

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Term
kinetics
Definition
refers to the rate at which a chemical reaction occurs (reaction rate)
Term
reaction rate
Definition
the change in concentration of a reactant of product over time
Term
rate law
Definition
the math expression relating the reaction rate to the rate constant and the reaction constant
Term
reaction orders
Definition
x & y
are partial reactions that state the control on the rate of the reaction by each of the reactants individually
Term
the overall reaction =
Definition
the sum of all the powers of all the partial reactions
Term
reasons for different reactions
Definition
0^0 = a catalyst, thus independent of [reactant]
1^0 = increase collision rate which is dependent of [reactant]
2^0 = a) increase in collision rate
b) more effective collisions
c) a lower activation energy
d) often exothermic so an even lower activation energy
Term
isolation method
Definition
how to determine the rate law by measuring the dependency of the reaction rate to the concentration of each reactant
Term
Savante Arrhenius described
Definition
quantitatively the collision theory
Term
Arrhenius Equation #1
Definition
k = Ae^(-Ea/RT)
Term
Arrhenius Equation #2
Definition
derived by taking the natural log of equation #1
ln (k) = ln (A-Ea/RT)
Term
Arrhenius Equation #3
Definition
determining Ea from two different T's and k's
ln (k1) = ln (A-Ea/RT1)
ln (k2) = ln (A-Ea/RT2)
ln (k1-k2) = Ea/R (ln( A-1/T1) - (ln(A - 1/T2))
Subtract these two and eliminate A
ln (k2/k1) = -Ea/R ((1/T2 - 1/T1))
Term
About reversible reactions (4)
Definition
1) may occur slowly or rapidly
2) only products are formed
3) reactant disappear to the point of LR
4) con use stoichiometry of balanced chemical equation to find the moles of the product
Term
About equilibrium reactions (5)
Definition
1) may occur slowly or rapidly
2) both products and reactants produced
3) stoichiometry not useful in finding moles
4) Equilibrium (keq)
5) ratio of reactants to products is useful in finding moles
Term
Equilibrium
Definition
dynamic state where two processes are occurring at the same time in a system until no farther net change occurs
Term
how to find moles in aequilibrium reaction
Definition
though stoichiometry is not useful, there is a relationship that there must be less of the initial reactants than products, thus a ratio of reactants to products is useful
Term
equilibrium constant (k)
Definition
a quantitative expression of the distribution of reactants vs products for a system at equilibrium
Term
k = 1
Definition
a 50:50 distribution of P and Rs
Term
k < 1
Definition
reactant concentration is greater than product concentration
Term
k > 1
Definition
product concentration is greater than reactant concentration
Term
concentration values used in k
Definition
solutions: molar concentrations (M)
pure liquids or solids: 1 (H2O = 55.5M)
gases: partial pressure (p*atm)
Term
how constant is k?
Definition
initial reactant concentration- no effect on k
pressure - no effect (except gases)
catalyst- no effect on k
temperature- does effect k; k is dependent on T
Term
Neutralization Reaction Summary:
Strong acid with strong base -
weak acid with strong base-
strong acid with weak base-
Definition
Strong acid with strong base- pH = 7.0
weak acid with strong base- pH > 7.0
strong acid with weak base- pH < 7.0
Term
pH for CH3COOH
Definition
8.72 pH
Term
main differences between strong acid and strong base versus weak acid and strong base (3)
Definition
1) weak acid & strong base starts at a higher pH
2) inflection point is harder to hit with a weak acid & strong base
3) equivalence point is greater than 7.0 with a weak acid & strong base
Term
Le Chatelier's Principle
Definition
1884
if stress is applied to a system in equilibrium, the system will behave in a manner that relieves the stress to restore equilibrium
Term
concentration
Definition
increase in concentration increases the rate of the reaction, so an increase in reactants --> R
Term
temperature
Definition
rate of the reaction increases about 2x for each 10C increase in temperature
Term
exothermic reactions
Definition
evolve heat since less energy is involved in bonds joining the product atoms together than required to bond reactant atoms
Term
endothermic reactions
Definition
absorb heat so forward reactions are favored when heat increases. this is due to more energy being required for forming the product bonds
Term
pressure
Definition
rate only effected when the reactants or products are gases. So an increase in pressure is equivalent to the increase in concentration.
Term
catalyst
Definition
though it is a reaction enhancer, there is no effect on reactant, so no effect on k
Term
in the spectrophotometic analysis of commercial aspirin lab we used _____ to analyze the percent composition of commercial grade aspirin
Definition
visible electromagnetic radiation, or white light
Term
Plank relationship equation
Definition
E = hv
Term
wavelength
Definition
distance between two crests of a wave
Term
frequency
Definition
the number of crests passing a given point in space each second
Term
wavelength is usually measured in
Definition
Angstroms ( 1A = 10^-10 m)
Term
polychromatic light
Definition
white light, or sunlight, composed of wavelengths of various colors
Term
monochromatic light
Definition
light of a single wavelength
Term
when white light comes in contact with an object it may be
Definition
1) reflected by
2) absorbed by
3) transmitted through
Term
light transmitted or reflected through an object will appear as
Definition
the complementary color
Term
Beer's Law equation
Definition
A = abc
A: absorbance
a: molar absorptivity
b: path length
c: concentration
Term
in Le Chat lab, the solution with the darkest color has the
Definition
highest concentration of FeSCN2+
Term
rate-controlling step
Definition
the slowest step in the mechanism
Term
molecularity
Definition
number of particles that collide
Term
in the Kinetic Study of an Iodine Clock Reaction lab, the order of reaction and the specific rate constant, k, was determined by
Definition
the Method of Initial Rates
Term
In the Kinetic Study of an Iodine Clock Reaction lab, the presence of I2 is detected by
Definition
observing the deep blue color it forms with the starch indicator
Term
In the Determination of an Equilibrium Constant lab, why is the cork wrapped in foil
Definition
to block the gas from escaping through the cork's large pores
Term
Decantation
Definition
The separation of a liquid from a solid by careful pouring, allow the solid to settle to the bottom of the container.
Term
Extraction
Definition
A separation process used when only one component of a mixture is soluble in a specific added solvent. After adding the solvent, the insoluble components can be recovered by removing the solvent using decantation or filtration.
Term
Why is water capable of dissolving other substances?
Definition
The reason for it is because of waters highly polar nature. The electrons in a water molecule aren't distributed equally but are concentrated near the oxygen atom and less concentrated near the hydrogen.
Term
Electrolyte
Definition
A substance that conducts electricity when dissolved in water. Strong electrolytes conduct strong ions whereas weak electrolytes do not.
Term
Solubility
Definition
The maximum mass of a solute that can dissolve in a mixture.
Term
Miscibility
Definition
When both solute and solvent are liquids
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