March 28, 2024, 12:38:32 PM
Forum Rules: Read This Before Posting


Topic: Calculate ?U, ?A, ?G..  (Read 5075 times)

0 Members and 1 Guest are viewing this topic.

Collegekid

  • Guest
Calculate ?U, ?A, ?G..
« on: November 30, 2005, 08:58:52 PM »
Two moles of water are allowed to vaporize at 100°C and 1 atm pressure.  The heat of vaporization of water at this pressure and temperature is 540 cal/g.  Calculate ?U, ?A, ?G, w, q, ?H, and ?S for this process in units of calories.  (This is just an example problem that I didn't know how to do.)

Offline mike

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1246
  • Mole Snacks: +121/-35
  • Gender: Male
Re:Calculate ?U, ?A, ?G..
« Reply #1 on: November 30, 2005, 09:01:24 PM »
What have you done so far?

Did you search this site? This might help a little:

http://www.chemicalforums.com/index.php?board=6;action=display;threadid=5471
There is no science without fancy, and no art without facts.

Offline Donaldson Tan

  • Editor, New Asia Republic
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 3177
  • Mole Snacks: +261/-13
  • Gender: Male
    • New Asia Republic
Re:Calculate ?U, ?A, ?G..
« Reply #2 on: December 01, 2005, 04:02:50 PM »
consider boiling water as an open system,

dH = Q + W = Q + VdP
Constant Pressure (dP=0): dH = Q

H = U + PV
Constant Pressure: dH = dU + PdV

Since at 100C, 1atm, water is at equilibrium, then
 ?S = Q/T

Mike's link will give you a clue on the value of dG.

To find ?A, try differentiating the expression for A
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Sponsored Links