141) The phase diagram for a substance is shown to the right. Answer the questions(a-f) regarding the diagram:(Circle one): A B Cc) Estimate the melting point at 30 atm:b) Circle the triple point on the graph.f) A student wants to measure the enthalpy of vaporization at standard pressure. Why is this impossible? OK: does not undergo liquid -> gas transition OR vaporization occurs at higher P than standard ORthe liquid phase does not exist at 1bar; always in gas phase at 1atm 1/2(Circle one) -105oC -15oC -5oC 50oC 200oCd) The phase transition when going from A to B is called(fill in the blank): _________________condensatione) Which is more dense (Circle one): solid or liquid?222222
CHEM 230 W16 PREP E2 keyp 35n-pentaneC5H12isopentaneC5H12neopentaneC5H12bp 36oC 27.7oC 9.5oCmp -129.8oC -159.9oC -16.6oCa) Which compound has the highest molar entropy at 25oC? (Circle one)n-pentane isopentane all are the same neopentane cannot be determinedb) Which compound has thehighest vapor pressure at 0oC? (Circle one)n-pentane isopentane all are the same neopentane cannot be determined154) For parts a-d consider the data about the isomers of pentane (C5H12) shown below and to the right.d) When the external pressure is lowered, the vapor pressure of n-pentane will become (Circle one) higher the samelower cannot be determinedc) Which compound will undergo the greatest change in entropy when heated from -20oC to 0oC? (Circle one)n-pentane isopentane all are the same neopentane cannot be determined33333182) Weather forcasters talk about relative humidity which is the ratio of the partial pressure of water in the air to the equilibrium vapor pressure of water at the same temperature. The vapor pressure of water at 32.2 oC (90oF) is 36 mm Hg.x36mmHg=0.9x=32.4mmHgPwater= mm Hg32.4a) On a sticky, humid day, when the relative humidity reaches 90% and the temperature is 90oF what is the partial pressure of water?b) Air at 90oF and 90% humidity is cooled to 31.0oC. Does any water condense? Yes NoBriefly explain your choiceThe vapor pressure of water at 31.0oC is 33.7 mm Hg.The partial pressure of water (32.4 mm Hg) is still less than the equilibrium vapor pressure of 33.7(Circle one)3
CHEM 230 W16 PREP E2 keyp 36P1 barT25oCP1 barT25oCP1 barT25oCP1 barT25oCABCDPlace the letter or letters of the phase diagrams that match the description in each of the boxes below:a) A substance that only sublimes (but does not melt and vaporize) under standard pressure.b) A substance whose solid is less dense than its liquid.c) The substance with the lowest standard melting point.A , CBA62 each180) Consider the four phase diagrams A-D shown below.209) Consider the carbon dioxide phase diagram.a)True or False: Solid carbon dioxide melts at ~ 220 K under standard pressure.b) True or False: Solid carbon dioxide sublimes at a pressure of 10 bar.