Posted by chemstudent on Thursday, February 5, 2009 at 12:01am.
A sample of 1.00 mol H2O(g) is condensed isothermally and reversibly to liquid water at 100°C. The standard enthalpy of vaporization of water at 100°C is 40.656 kJ mol−1. Find w, q, ∆U, and ∆H for this process.

I can solve for ∆H: n * standard ∆H * 1 because reverse of vaporization.
40.656 kJ
I can solve for ∆U:
∆H = ∆U + ∆n(gas)*RT
40.656 = ∆U + 1 * R * 373.15K
∆U = 37.55 kJ
Now, how do I figure out w and q
I know that
∆U = q + w
but beyond that, how do I solve?

Chemical Engineering  Alex, Saturday, December 1, 2012 at 6:10pm
The pressure is constant, and so the heat at constant pressure is qp =  dH vaporization. W=pdV and so since p=pext=1atm and dV = (vf  vi) = vliquid  vvapor, we'll say that since the volume of the vapor is significantly greater than that of the liquid, then vfvi is approximately equal to volume of vapor =  nRT/pext. Solve for these and then you get dU.

chemistry  Karl, Monday, September 28, 2015 at 9:59pm
Well, the pressure here is not constant, but the temperature is. Reversible implies that there are infinitesimal changes in certain parameters.
For isothermal, reversible systems
delta H=0
delta U=0
q=w
and w=nRTln(Vf/Vi)
You can find your Vf by using the density constant for liquid water which s essentially 1.0 g/mL.
I used SATP laws for an ideal gas to find the volume of water at room temp. Then I converted to the volume at higher temp using the relation V1/T1=V2/T2. Hope this works.
Answer This Question
Related Questions
 Chemistry  Science (Dr. Bob222)  Hydrazine is used as a rocket fuel because ...
 chemistry  7. (a) Determine the crystal lattice energy for LiF(s) given that ...
 AP Chemistry  A 34.05 gram liquid sample of an unstable compound is deposited ...
 AP Chemistry  DrBob222 PLEASE HELP Hf of CO2 = 393.5 kJ/mol Hf of H2O = 285.8...
 chemistry  Calculate the standard entropy change for the reaction of calcium ...
 chemistry  3.5 moles of steam at 100 C are condensed at 100 C and the resulting...
 Chemistry  1.What is the molar heat of vaporization of water, given the ...
 chemistry  What is the ∆G for the following reaction under standard ...
 chemistry  Calculate the heat of formation of water from its constituent ...
 Chemsitry  What is the ∆G for the following reaction under standard ...
More Related Questions