Exam 1 Study Guide
Exam 1 Study Guide 4300
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This 6 page Study Guide was uploaded by Justin Hsu on Saturday September 12, 2015. The Study Guide belongs to 4300 at University of Missouri - Columbia taught by Michael Henzl in Summer 2015. Since its upload, it has received 961 views. For similar materials see Physical Chemistry of Biological Systems in Biochemistry at University of Missouri - Columbia.
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Date Created: 09/12/15
Biochem 4300 Fall 2015 Exam 1 Study Guide Chapter 1 1 2 3 U 10 11 12 13 14 15 16 17 18 19 20 The exact differentials are the state variables P V U H S G The inexact differentials are the path variables q W Heat and work are responsible for all energy exchanges between system and surroundings Heat produces or utilizes random motion of atoms in the surroundings Work produces or utilizes uniform motion of atoms andor molecules in the surroundings Nuclear electronic vibrational rotational translational and potential energy contribute to the internal energy of a system The internal energy of an ideal gas depends solely on temperature The 1st law for a closed system AU q W Potential energy is possessed by a system virtue of its position while kinetic energy is possessed by virtue of its motion The following are extensive properties mass m volume V enthalpy H entropy S Energy E and amount mol The following are intensive properties temperature T pressure P density mV ratio of two extensive properties and all molar properties For a perfect gas that expands isothermally against an external pressure of 1 bar qgt0 wlt0 AU and AH0 For a perfect gas that expands adiabatically against an external pressure of 1 bar q0 and w AU and AH are lt0 A reversible process distinguishes from an irreversible process in that in a reversible process the system is at equilibrium with the surroundings When we see two samples reversibly compressed to the same final volume one conducted isothermally and the other conducted adiabatically the sample that is conducted adiabatically will have the higher final temperature and pressure For a system comprised of a very large number of atomsmolecules the most probable distribution of energy is described by the Boltzmann Distribution The magnitude of heat capacity is indicative of the number of ways that energy can be distributed in a system Volume heat capacity describes the temperaturedependence of the internal energy Pressure heat capacity describes the temperaturedependence of enthalpy Nonlinear triatomic gases have the largest heat capacity Linear and diatomic gases have the 2nd largest but monatomic gases have the smallest heat capacity 21 22 23 24 25 26 27 28 29 30 31 32 33 To find the heat capacity at low temperatures you do not add vibrational heat capacity because it is not observed Instead add translational and rotational At high temperatures add translational rotational and vibrational The compressibility factor Z is the ratio or the molar volume to the ideal molar volume ZVNidPVRT For an ideal gas Z1 at all pressures For real gases at higher pressures Zgt1 and roughly proportional to pressure which makes it a finite size while at lower pressures Zlt1 which makes the gas intermediate AU is directly measured in a bomb calorimeter AH directly is directly measured in an isobaric ame calorimeter Differential scan calorimeter is useful for studying phasetransitions in biolymers The most reduced state of the component carbon atoms have the highest specific enthalpy of combustion alkanesalcoholsalkenes In 2H2 g 02 g I H20 1 AH is lt AU making this reaction exothermic We need to know heat capacity AC in order to calculate the enthalpy change for a chemical reaction at temperature T2 given the value at T1 Hess s Law states that the standard enthalpy of a reaction is the sum of the standard enthalpies of the reactions into which the overall reaction can be divided The steps to estimate the enthalpy change for a chemical reaction given a table of bond energies are vaporize decompose reassemble and condense Given the reaction aA bB cC dD the expressions for ACp is Cpc de Cp1 Cpb The enthalpy change that accompanies formation of a mole of substance from its elements in their reference is called the expression Chapter 2 1 The steps in a Carnot cycle are isothermal expansion adiabatic expansion isothermal compression and adiabatic compression Heat is exchanged only in isothermal expansion and isothermal compression Detailed consideration of the Carnot cycle led to the recognition that the entropy is a state function and the complete conversion of heat to work is prohibited by the Second Law In a Carnot engine some heat is converted to work but the remaining heat is transported to a cold reservoir The second law of thermodynamics states that the entropy of an isolated system always decreases during a spontaneous process In a spontaneous process the entropy of a system always decreases The entropy of a system is a measure of the energy that is unavailable to do work on the surroundings ASsystem0 for a spontaneous cyclic process 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 The efficiency of a Carnot heat engine represents the upper bound to the efficiency of an internal combustion engine because it is a reversible process The Carnot heat engine will have the highest efficiency if 1ThTcgt500 In a Carnot refrigerator qhot is negative qcold is positive and wcycle is positive The entropy change accompanying the isothermal expansion of an ideal gas at 273K from 2L to 4L against an external pressure of 1 atm is greater than the entropy change for the identical process conducted at 373K The entropy of an ideal gas decreases when the pressure is increased Spontaneous processes are driven by the tendency for matter and energy to disperse The efficiency of a heat engine is equal to the ratio of the work to the heat transfer The entropy change associated with a phase transition equals the AH divided by T The entropy of a perfectly crystalline substance is zero at T0 Gibbs free energy specifies the maximum nonexpansion work that can be performed by a system A species having both hydrophobic and hydrophilic regions are amphipathic or amphiphilic For any spontaneous process if AH is positive AS is negative AGlt0 A pure crystalline substance for which S at 0 at 0K has residual entropy When the moles of gas decrease from reactants to products the entropy AS is negative An example of a spontaneous process Adiabatic expansion of an ideal gas into a vacuum Pressure must be constant when qAH and CAHAT C represents heat capacity When AS qT q must be reversible For an ideal gas AH AE AnRT There are no restrictions in AU q W and W pextAV ASfusion and ASVporim on are always positive quantities because qfus and qv1p gt0 When a sample of liquid is converted reversibly to its vapor at its normal boiling point AT AP and AG 0 The heat q and work w differs when a sample of liquid is vaporized isothermally and completely into an evacuated chamber just large enough to hold the vapor at 1atm pressure and another identical sample is vaporized reversibly Chapter 3 1 The triple point is the point on the phase diagram at which solid liquid and vapor phases are in equilibrium The crital point is the point at which the pressure and temperature at which the distinction between liquid and vapor phase ceases to exist Sublimation is the phasetransition that occurs when the temperature of a substance is raised at a pressure below the triplepoint pressure 10 11 12 13 14 15 16 17 18 19 20 In contrast to most substances the slope of the solidliquid boundary in the phase diagram for water has a negative slope because The solid phase of water have a lower density than the liquid phase because Subjectin the liquidphase to high pressure encourages solidification because the volume of a solid is lower than liquid so the energy decreases The isotherms for real gases only resemble those for an ideal gas at temperatures above the critical point At temperatures below the critical point When the pressure is increased the pV curve exhibit horizontal regions corresponding to the condensation 1 mol of liquid water is reversibly converted to ice at 0 C at 1 atm pressure by slow transfer of heat to the surroundings a In this process the system entropy will decrease b The accompanying Gibbs energy will be zero c The enthalpy of the system will decrease d The entropy of the surrounding will increase The temperature range over which the liquid phase of a substance can exist is bounded by the triple and the critical point The doublehelical secondary structure of nucleic acids is stabilized by hydrogen bonds and T e39 interactions The isotherms in a pV diagram for a real gas resemble those for an ideal gas only when the temperature is above the critical point At temperatures below the critical point the isotherm in a pV diagram for a real gas includes a horizontal segment corresponding to condensation Under certain conditions a protein will adopt a compact partially unfolded form referred to as a molten globular Solvent entropy and weak enthalpic interactions contribute to the stability of a folded protein at physiological temperatures Salt bridges Hbonds dipoledipole and disulfide bonds are the enthalpic contributions to protein stability at physiological temperatures Raoult s law states that the partial pressure of a volatile substance in an ideal solution is proportional to the mole fraction of the substance and the vapor pressure of the pure substance Henry s law states that the partial pressure of a volatile solute in an ideal dilute solution is proportional to its mole fraction A solution of solute B in solvent A that obeys Raoult s law over the entire composition range is called an ideal solution A solution of solute B in solvent A that obeys Henry s law over the entire composition range is called an ideal solution A solution of solute B in solvent A that obeys Henry s law at sufficiently low solute concentrations is called an ideal dilute solution 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 If a twocomponent solution obeys Raoult s law over the entire composition range then AGmiX must be entirely entropic The partial molar Gibbs energy is commonly called the chemical potential The chemical potential is a measure of the ability of a substance to drive a chemical or physical process In a mixture of gases the partial pressure of each gas is proportional to its mole fraction Pentanehexane is a binary mixture that would most closely approximate an ideal solution The molar scale re ects moles per kg of solvent while the molar concentration re ects the moles of a substance per liter of solution The molal scale is preferred over the molar scale for precision calculations because 1 the mass can be measured more precisely than volume and 2 molal concentrations are temperatureindependent The physical basis for all colligative properties is that the changes in solvent behavior depends on the number of solute particles present but is independent of the identity of the species The consequences of the addition of a nonvolatile solute to pure solvent are the depression of solvent vapor pressure depression of the solvent freezing point elevation of solvent boiling point and the development of osmotic pressure Adding the solute to a pure solvent raises the boiling point of the solvent but lowers the freezing point because the solute lowers the chemical potential of the solvent but the vapor and the pressure remained pure Osmosis refers to the passage of pure solvent through a semipermeable membrane into an adjacent solution The Donnan Equilibrium describes the distribution of ions in two solutions one of which contains a polyelectrolyte separated by a semipermeable membrane The effective concentration of a substrate is the thermodynamic activity Nonideal behavior of biopolymers is a consequence of their osmotic pressure For an ideal solution the free energy of mixing is entirely entropic The activity of each component in an ideal solution is equal to its mole fraction The activity of each component in a nonideal solution is proportional to its mole fraction The proportionality constant is the activity coefficient V Redoing the numerical problems on the numerical problems handouts is also recommended If you can also do the book problems as assigned in the Lecture handout If you have a different teacher here are the assigned book Atkins problems from lecture handouts that will be on this test if you are in a cramming session you do not have to do all of them Chapter 1 111 112 113114 116117 118120 112 122 123124 126127 128 129131 133 134 135 136 137 141 142 143 Chapter 2 28 29 210 212 213 214 215 217 218 220 221 222 223 226 227 228 229 Chapter 3 310 312 313 314 317 319 322 323 324 325 326 329 333
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