# Chemistry 132 Midterm

 kinetics
 refers to the rate at which a chemical reaction occurs (reaction rate)
 reaction rate
 the change in concentration of a reactant of product over time
 rate law
 the math expression relating the reaction rate to the rate constant and the reaction constant
 reaction orders
 x & yare partial reactions that state the control on the rate of the reaction by each of the reactants individually
 the overall reaction =
 the sum of all the powers of all the partial reactions
 reasons for different reactions
 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
 isolation method
 how to determine the rate law by measuring the dependency of the reaction rate to the concentration of each reactant
 Savante Arrhenius described
 quantitatively the collision theory
 Arrhenius Equation #1
 k = Ae^(-Ea/RT)
 Arrhenius Equation #2
 derived by taking the natural log of equation #1ln (k) = ln (A-Ea/RT)
 Arrhenius Equation #3
 determining Ea from two different T’s and k’sln (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 Aln (k2/k1) = -Ea/R ((1/T2 – 1/T1))
 1) may occur slowly or rapidly2) only products are formed3) reactant disappear to the point of LR4) con use stoichiometry of balanced chemical equation to find the moles of the product
 1) may occur slowly or rapidly2) both products and reactants produced3) stoichiometry not useful in finding moles 4) Equilibrium (keq)5) ratio of reactants to products is useful in finding moles
 Equilibrium
 dynamic state where two processes are occurring at the same time in a system until no farther net change occurs
 how to find moles in aequilibrium reaction
 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
 equilibrium constant (k)
 a quantitative expression of the distribution of reactants vs products for a system at equilibrium
 k = 1
 a 50:50 distribution of P and Rs
 k < 1
 reactant concentration is greater than product concentration
 k > 1
 product concentration is greater than reactant concentration
 concentration values used in k
 solutions: molar concentrations (M)pure liquids or solids: 1 (H2O = 55.5M)gases: partial pressure (p*atm)
 how constant is k?
 initial reactant concentration- no effect on kpressure – no effect (except gases)catalyst- no effect on k temperature- does effect k; k is dependent on T
 Neutralization Reaction Summary: Strong acid with strong base – weak acid with strong base- strong acid with weak base-
 Strong acid with strong base- pH = 7.0weak acid with strong base- pH > 7.0strong acid with weak base- pH < 7.0
 pH for CH3COOH
 8.72 pH
 main differences between strong acid and strong base versus weak acid and strong base (3)
 1) weak acid & strong base starts at a higher pH2) inflection point is harder to hit with a weak acid & strong base3) equivalence point is greater than 7.0 with a weak acid & strong base
 Le Chatelier’s Principle
 1884if stress is applied to a system in equilibrium, the system will behave in a manner that relieves the stress to restore equilibrium
 concentration
 increase in concentration increases the rate of the reaction, so an increase in reactants –> R
 temperature
 rate of the reaction increases about 2x for each 10C increase in temperature
 exothermic reactions
 evolve heat since less energy is involved in bonds joining the product atoms together than required to bond reactant atoms
 endothermic reactions
 absorb heat so forward reactions are favored when heat increases. this is due to more energy being required for forming the product bonds
 pressure
 rate only effected when the reactants or products are gases. So an increase in pressure is equivalent to the increase in concentration.
 catalyst
 though it is a reaction enhancer, there is no effect on reactant, so no effect on k
 in the spectrophotometic analysis of commercial aspirin lab we used _____ to analyze the percent composition of commercial grade aspirin
 visible electromagnetic radiation, or white light
 Plank relationship equation
 E = hv
 wavelength
 distance between two crests of a wave
 frequency
 the number of crests passing a given point in space each second
 wavelength is usually measured in
 Angstroms ( 1A = 10^-10 m)
 polychromatic light
 white light, or sunlight, composed of wavelengths of various colors
 monochromatic light
 light of a single wavelength
 when white light comes in contact with an object it may be
 1) reflected by 2) absorbed by 3) transmitted through
 light transmitted or reflected through an object will appear as
 the complementary color
 Beer’s Law equation
 A = abcA: absorbance a: molar absorptivity b: path lengthc: concentration
 in Le Chat lab, the solution with the darkest color has the
 highest concentration of FeSCN2+
 rate-controlling step
 the slowest step in the mechanism
 molecularity
 number of particles that collide
 in the Kinetic Study of an Iodine Clock Reaction lab, the order of reaction and the specific rate constant, k, was determined by
 the Method of Initial Rates
 In the Kinetic Study of an Iodine Clock Reaction lab, the presence of I2 is detected by
 observing the deep blue color it forms with the starch indicator
 In the Determination of an Equilibrium Constant lab, why is the cork wrapped in foil
 to block the gas from escaping through the cork’s large pores
 Decantation
 The separation of a liquid from a solid by careful pouring, allow the solid to settle to the bottom of the container.
 Extraction
 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.
 Why is water capable of dissolving other substances?
 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.
 Electrolyte
 A substance that conducts electricity when dissolved in water. Strong electrolytes conduct strong ions whereas weak electrolytes do not.
 Solubility
 The maximum mass of a solute that can dissolve in a mixture.
 Miscibility
 When both solute and solvent are liquids
x

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