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The standard entropy of vaporization is ob-tained fromRlnP1P0¶=-ΔH◦vapT1+ ΔS◦vapΔS◦vap=RlnP1P0¶+ΔH◦vapT1=8.314JK·mol¶ln58 Torr760 Torr¶+28310 J/mol298.15 K= 91.6683JK·mol.The standard free energy of vaporization isΔG◦vap= ΔH◦vap-TΔS◦vap= 28310 J/mol-(298.15 K)91.6683JK·mol¶= 979.118 J/mol.005(part 1 of 1) 10 pointsMethane(CH4)formsamolecularsolid.What type of forces hold it in a solid con-figuration?I) London forcesII) dipole-dipole forces
Thompson, Margaret – Homework 1 – Due: Sep 11 2007, 11:00 am – Inst: James Holcombe3III) hydrogen bonding1.II only2.III only3.I and II only4.I, II, and III5.II and III only6.I onlycorrectExplanation:Solid methane is held together only by Lon-don forces.006(part 1 of 1) 10 pointsWhich one of the following statements is NOTapplicable to molecular solids?1.Molecular solids have relatively low melt-ing points.2.Molecular solids are usually excellent con-ductors of electric current.correct3.Molecular solids are soft compared tocovalent solids.Explanation:Molecular solids consist of molecules heldtogether by weak intermolecular forces; thusthey are soft and have low melting points.007(part 1 of 1) 10 pointsWhen a gas expands into a vacuum,w= 0.1.Truecorrect2.FalseExplanation:008(part 1 of 1) 10 pointsConsider the following classic:Humpty Dumpty sat on a wall...Humpty Dumpty had a great fall...All the king’s horses and all the king’s menCouldn’t put Humpty back together again.Poor Humpty Dumpty has fallen prey to aparticular law of nature know as1.conservation of momentum.2.the 2nd Law of Thermodynamics.cor-rect3.catch-22.4.Murphy’s Law.5.the 1st Law of Thermodynamics.Explanation:The Second Law of Thermodynamics statesthat in spontaneous changes,the universetends towards a state of greater disorder.Humpty spontaneously fall and broke into adisordered pile of eggshell.009(part 1 of 1) 10 pointsIs an exothermic process spontaneous?1.no, never2.sometimescorrect3.yes, alwaysExplanation:Sponteneity is based on the value of ΔG.ΔG= ΔH-TΔS.ΔGis dependent notonly on the value of ΔH, but alsoTand ΔS.010(part 1 of 1) 10 pointsCalculate the change in entropy of a large pailof water after 200 J of energy is reversiblytransferred to the water at 20◦C.1.+0.733 J·K-12.-0.683 J·K-13.-0.733 J·K-14.-200 J·K-15.+0.683 J·K-1correctExplanation:
Thompson, Margaret – Homework 1 – Due: Sep 11 2007, 11:00 am – Inst: James Holcombe4011(part 1 of 1) 10 pointsThe thermite reactionFe2O3+ 2 Al(s)-→2 Fe(s) + Al2O3(s)used in some welding applications has thefollowing enthalpy and entropy changes at298.15 K:ΔH0=-871.7 kJ/molΔS0=-0.038 kJ/mol·KAssuming ΔSand ΔHare constant, calculateΔGat 448 K. Your answer must be within±0.5%.