# First law of thermodynamics and work done

1. May 31, 2009

### fly_bo1

Two kilograms of water at 100oC is converted to steam at 1 ATM. Find the work done (in J). (The density of steam at 100oC is 0.598 kg/m3.)

a. 4.6 x 104
b. 3.4 x 104
c. 1.2 x 105
d. 2.1 x 104
e. 3.4 x 105

I'ved use the integration holding volume as a variable. However, I dont know why im not getting the right answer.

2. Jun 1, 2009

### Andrew Mason

You don't have to do an integration. Assume that the change in volume from water to steam occurs at 1 Atm external pressure and that the steam is created gradually. Pressure is constant, so $W = \int PdV = PV$ (assume initial volume is 0).

AM

PS Welcome to PF, btw.