# Homework Help: Change in Entropy

1. Feb 7, 2010

### ihearyourecho

1. The problem statement, all variables and given/known data

Find the change in entropy when 2.00 kg of water at 100 degrees C is boiled away to steam at 100 degrees C. Give your answer in kJ/K

2. Relevant equations
deltaS=Q/T
Q=m*Lvaporization

3. The attempt at a solution
Q=m*Lvaporization
Q=2 kg * 22.6*10^5 J/kg
Q = 4.52x10^6 J

I'm not not sure how to find T though since it's at 100 degrees and going to 100 degrees...

Thanks!

2. Feb 8, 2010

### ihearyourecho

There's a good deal of views on here, does no one know how to do this? ;)

3. Feb 8, 2010

### Andrew Mason

T is given. All you have to do is put it in the correct scale. The denominator in $\Delta Q/T$ is the absolute temperature at which the heat flows into the water.

AM

4. Feb 8, 2010

### ihearyourecho

Oh, I thought I had to do something more complicated with the T. Thanks!