PS5_2011Ans - Name Section Rec TA Ch 1b Solution Set for...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Name: Ch 1b, Solution Set for Problem Set Five Section: Sid e 1 of 12 Due Friday, Feb. 12, 2010 Rec TA: at 4 PM in the Drop Box 1 . En t halpy Chang e & Pha s e Tran s i t ion s (24 poin ts ) Calculate ' H (units: kJ) for this process: Process Start: 2.00 mol of steam at 130 q C Process End: 2.00 mol of ice at ± 15.0 q C Use ǻ ƨ f u s ion = 6.03 kJ mol -1 and ǻ ƨ vap = 40.7 kJ mol -1 for the specific molar heats of fusion and vaporization, respectively, at their transition temperatures. (NOTE: 6RPHWLPHV \RX¶OO VHH D FDUDW RYHU WKH V\PERO IRU HQWKDOS\ ZKHQ LW KDV XQLWV RI HQHUJ\ SHU XQLW PROH DQG LW¶V FDOOHG VSHFLILF PRODU HQWKDOS\² 2WKHU WLPHV SHRSOH ZL ll just use the same symbol, H (without the carat), for enthalpy, specific molar enthalpy and specific mass enthalpy ± watch the units c lo s e ly to determine if you have to multiply by the number of moles or the mass.) You may assume that specific molar heat capacity (see Table below) is independent of temperature for each phase. H e at c apa c ity ( c P ) J mol -1 K -1 Ice 38.0 Liquid water 74.5 Steam 36.0 You may treat steam as an ideal gas, and you may assume the process is isobaric. Solu t ion Break the process into five steps, all occurring at 1.00 atm. ( 5 poin ts for clearly stating these states: picture/graph or words are OK) State A o State B: cool steam from 130 q C to 100 q C State B o State C: condense steam at 100 q C State C o State D: coolliquid water from 100 q C to 0.00 q C State D o State E: freeze water at 0.00 q C State E o State F: cool ice from 0.00 q C to ± 15.0 q C A o B: cool steam from 130 q C to 100 q C H A o B = nc P , steam T ( 2 poin ts ) ' o B A H (2.00 mol) ( 36.0 J/K/mol )( 100 q C - 130 q C) ' o B A H -2160 J ( 1 poin t )
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Name: Ch 1b, Solution Set for Problem Set Five Section: Sid e 2 of 12 Due Friday, Feb. 12, 2010 Rec TA: at 4 PM in the Drop Box B o C: condense steam at 100 q C H B o C = n Ö H vap ( 2 poin ts ) ' o C B H (2.00 mol)(-40.7 kJ/mol) ' o C B H -81400 J ( 1 poin t ) C o D: cool liquid water from 100 q C to 0.00 q C T n c H liquid P D C ' ' o , ( 2 poin ts ) ' o D C H (2.00 mol) ( 74.5 J/K/mol )( 0.0-100.0 q C) ' o D C H -14900 J ( 1 poin t ) D o E: freeze water at 0.00 q C H D o E = n Ö H fus ( 2 poin ts ) ' o E D H (2.00 mol)(-6.03 kJ/mol) NO T E: s hould b e 6 . 01 kJ / mol ' o E D H -12100 J ( 1 poin t ) E o F: cool ice from 0.00 q C to ± 15.0 q C H E o F = nc P , ice T ( 2 poin ts ) ' o F E H (2.00 mol)(38.0 J/K/mol)( ± 15.0-0.0 q C) ' o F E H -1140 J ( 1 poin t ) Overall Process (A o F) F E E D D C C B B A F A H H H H H H H o o o o o o ' ± ' ± ' ± ' ± ' ' ' ( 1 poin t ) ' H -2160 J + -81400 J + -14900 J + -12100 J + -1140 J ' H -111700 J H = 111.7 kJ ( 3 poin ts t o t al : 2 points for value, 1 point for sig figs) NO T E: fu s ion e nthalpy for wat e r = 6 . 01 kJ / mol a s s tat e d in th e probl e m , whi c h giv e s th e final an s w e r a s -111 . 6 kJ . A note about sig figs: There are four significant figures in the answer because when added, the least accurate value is significant to the hundreds place.
Image of page 2
Name: Ch 1b, Solution Set for Problem Set Five Section: Sid e 3 of 12 Due Friday, Feb. 12, 2010 Rec TA: at 4 PM in the Drop Box 1RWH³ , GLGQ¶W FRQYHUW WHPSHUDWXUH IURP &HOVLXV WR .HOYLQ HYHQ WKRXJK WK e denominator for the heat capacity has units of Kelvin. As long as you deal with t e mp e ra t ur e diff e r e n ce s
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern