Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: helpmeimnoob on January 02, 2008, 08:58:47 PM

Title: another phase change problem
Post by: helpmeimnoob on January 02, 2008, 08:58:47 PM

ok, once again, i need help with another phase change problem:

what is the amount of energy that must be removed from 125.0 grams of water @ 35.7 degrees C when converted to ice @ 0.0 degrees C?

Ok, so I got this far:

4.18J/1g x deg C     X    125g    X 35.7 deg C = 18653.25

Then...

(something i dont know)/(something i dont know) x 125g = (something I dont know)

Can someone plugg the items in?

Title: Re: another phase change problem
Post by: Sev on January 02, 2008, 09:09:43 PM

L_f of water is 334Jg^-1.  So how much energy to convert 125g of water (at 0⁰C) to ice?

Title: Re: another phase change problem
Post by: Alpha-Omega on January 02, 2008, 10:54:26 PM

This is called Latent Heat:

•   Energy = mass X latent heat of fusion


You have everything you need Sev gave you the Latent Heat for water.