posted by Kay on .
CFCs such as CF2Cl2 are refrigerants whose use has been phased out because their destructive effect on Earth's ozone layer. The standard enthalpy of evaporation of CF2Cl2 is 17.4 kJ/mol, compared with change in H(vapor)=41kJ/mol for liquid water. How many grams of liquid CF2Cl2 are needed to cool 130.8g of water from 49.4 to 29.4 Celcius? The specific heat of water is 4.184 J/(g*C)
q needed to cool water is
q = mass water x specific heat water x (Tfinal-Tinitial)
Then 17,400 J/mol x ?mol = q to cool water by 20 C.
Solve for moles CF2Cl2 and convert to grams.