Homework Help: chemistry

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 vf-vi is approximately equal to -volume of vapor = - nRT/pext. Solve for these and then you get dU.

Answer this Question

Related Questions

Chemistry - How much energy (in kilojoules) is released when 12.8 g of steam at ...
chemistry - 3.5 moles of steam at 100 C are condensed at 100 C and the resulting...
chemistry - How much energy (in kilojoules) is released when 12.3g of steam at ...
Chemistry - 1.What is the molar heat of vaporization of water, given the ...
chemistry - How much energy (in kilojoules) is released when 12.3g of steam at ...
chemistry - How much energy (in kilojoules) is released when 12.3g of steam at ...
Chemistry - How much heat is released when 75.0 g of steam at 100.0°C is ...
chemistry - How much energy (in kJ) is released when 16.4 g of steam at 121.5 ...
Chemistry - The heat capacity of liquid water is 4.18 J/g·°C and the ...
Science - Calculate the quantity of energy required to change 3.00 mol of ...

For Further Reading

First Name:
School Subject:
Answer: