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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: BetaAmyloid on January 10, 2010, 05:04:36 PM

Title: Heat of Vaporization
Post by: BetaAmyloid on January 10, 2010, 05:04:36 PM

Compounds like CCl2F2 are known as chlorofluorocarbons, or CFCs. These compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful to the environment. The heat of vaporization of CCl2F2 is 289 J/g. What mass of this substance must evaporate to freeze 120. g of water initially at 15°C? (The heat of fusion of water is 334 J/g; the specific heat of water is 4.18 J/g-K.)

I have no idea where to start...we never covered this - can someone give me a place to start? A Hint?

Title: Re: Heat of Vaporization
Post by: MrTeo on January 11, 2010, 11:41:31 AM

First of all you have to cool down the water to 0ºC and then take away the amount of energy needed to freeze it: all the heat absorbed by CCl₂F₂ makes it volatilize. You only need to equal this value with the total energy taken away from water and the job's done.  ;)