CHM1046 FINAL EXAM PART I Chapter 11 11 2 different Intermolecular Forces forces that determine the phase S or L of molecules exists b w molecules weaker than INTRAmolecular forces Hvap Hfus Hsub BP Surface Tension Viscosity Induced Dipole Induced Dipole Dispersion exists in all molecules o strength larger the electron larger the dispersion force o larger the molecular mass larger the dispersion force Dipole dipole b w polar covalent molecules Dipole Induced Dipole b w polar and nonpolar molecules Ion dipole b w ionic and polar molecules o depends on ionic charge and size o strength cation anion Ion Ion b w ionic molecules o forces increase as ionic charge increases and decreases as ionic radius increases Ion Induced Dipole b w ionic and NONpolar molecules o depends on charge size and polarizability incr with the incr in of e or MW Hydrogen Bonding special type of dipole dipole b w H atoms in a polar bond N H O H F H and electronegative O N F atoms o depends on interaction b w electrons on the EN atom and H o BP stronger intermolecular forces increase BP Van Der Waals Forces Water is special very polar H bonds ice is less dense than liquid water Oxygen makes 2 H bonds with H2 o each H makes 1 H bond with O 11 3 Chapter 12 12 2 Solubility measure of how much solute can dissolve in specific solvent at specific temp like dissolves like each other o two substances with similar intermolecular forces are likely to be soluble in o polar solutes dissolve in polar solvents way better than nonpolar o nonpolar dissolve in nonpolar o ionic soluble polar process called sol solvent orient in certain way around the ions Miscibility ability of two or more liquids to dissolve mix homogeneously at any Solvation dissolution attraction and association of molecules of a solvent with proportion ex ethanol water molecules of a solute Chapter 13 13 5 Mechanism set of elementary steps o every reaction has one o to find the overall reaction add up elementary steps o Elementary steps in these are species called intermediates compound that cancels out at the end not found in balanced equation formed in first step 1 product used in step 2 last step reactant EX H2O2 aq I aq H2O l IO aq slow IO aq H2O2 aq H2O l O2 g I aq fast o Intermediate IO some elementary steps are slow and some are fast slowest step determines rate law rate determining step RDS this means that the stoichiometry of reactants determine rate law A products rate k A A B products rate k A B 2A products rate k A 2 every reaction mechanism had energy diagram highest Ea slowest step Molecularity classification of an elementary reaction based on the number of molecules or atoms on the reactant side of the chemical equation o unimolecular bimolecular termolecular 13 6 Catalyst substance that increase the rate of a chemical reaction without being consumed o always consumed and then reforms reacts in step 1 then reforms in step 2 or last step o not included in balanced equation o since the catalyst is in the RDS it often appears in the rate law o the presence of a catalyst does not affect the net energy difference between the reactants and products Chapter 14 14 1 14 2 2 types of reactions o complete rxns o rxns at equilibrium equilibrium constant K o tells us if more products or reactants are present at equilibrium o if rxn will proceed forwards or backwards o how to calculate the equilibrium concentrations equilibrium constant does not have units ONLY DEPENDS ON AQUEOUS AND GAS COMPOUNDS Kc depends on concentration of species that are aqueous or gas Kp depends on pressure of gases only o n sum of coefficients or products sum of coefficients of reactants Kc Kp are UNITLESS Kp Kc RT n o T is in K o R is 0 0821 ex If we have concentration at equilibrium we can calculate Kc NH4Hs s NH3 g H2S g The partial pressures of each components is 0 265 atm at equilibrium calculate Kp Kc 1 Pproducts Preactants 2 write down expression of Kp 3 Kp Kc RT n n 2 a Kp PNH3 PH2S Kp 0 0205 0 265 0 070 a Kc Kp RT 2 0 070 0 0821 395 2 b Kc 6 66x10 5 multiple equilbria o A B C D K1 C D E F K2 A B E F K K K1 x K2 H2CO3 aq H aq HCO3 aq k1 HCO3 aq H aq CO3 2 k2 overall H2CO3 2H CO3 2 k k1 k2 HCO3 k H HCO3 H HCO3 H CO32 H CO32 H CO3 H k1 k2 HCO3 CO32 o if a rxn can be expressed as the sum of two or more rxns the equilibrium constant for the overall rxn is given by the product of the equilibrium constants of the individual rxns o Writing equilibrium constants expressed in M condensed phase M or in atm gaseous concentrations of pure solids pure liquids and solvents do not appear in the equilibrium constant expressions equilibrium constant is a dimensionless quantity in quoting a value for the equilibrium constant you must specify the balanced equation and the temperature if a rxn can be expressed as a sum of two or more rxns the equilibrium constant for the overall rxn is given by the product of the equilibrium constants of the individual rxns Hess s Law o if you reverse an equation invert the equilibrium constant A 2B 3C Kforward C 3 A B 2 3C A 2B Kreverse A B 2 C 3 1 Kforward constant to the same factor nA 2nB 3nC K C 3 A n B 2n Kn o if you multiply the coefficients in the equation by a factor raise the equilibrium o if you add two or more individual chemical equations to obtain the overall equation multiply the corresponding equilibrium constants by each other to obtain the overall equilibrium constant A 2B K1 B 2 A 2B 3C K2 C 3 B 2 A 3C Koverall C 3 A Koverall K1 K2 14 5 if a system is at equilibrium a stress is added then system will shift either R or L to reestablish equilibrium N2 g 3H2 g 2NH3 g Keq 2 37x10 3 o system at equilibrium add N2 to system reaction will shift to the right o any stress produce shifting but K is constant removed H2 g what happen o system will shift to the left removed NH3 o the system will shift to the right Volume is inversely proportional to pressure o meaning if volume pressure if volume pressure volume pressure is related to ONLY the gas o ex 1 N2O4 g 2NO2 g R 1 mole P 2 moles o volume pressure 1 the system will start producing more of moles of gas not sol liq aq 2 we compare the of moles stoichiometry in R P 3 the system will shift towards more of moles products in this rxn o volume pressure the …
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