7. 1,1-difluoroethane, commercially known as HFC 152a and having a molecular formula of C2H4F2 , is a refrigerant now used as a replacement for the many CFCs that are no longer allowed because they are so devastating to the ozone layer. Refrigerants generally work to cool things by absorbing energy and using that energy to evaporate. (The vapor is carefully contained, pumped to a remote location—like behind the refrigerator—and then the energy is released to metal coils that heat the air as the HFC 152a condenses back down to a liquid, where it is pumped back to the cooling chamber to start the cycle again.) The enthalpy of vaporization for HFC 152a is 20.4 kJ/mol. How many grams of HFC 152a are needed to cool 200.0 g of water from 50.0 °C to 40.0 °C? You will need the heat capacity of liquid water.
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
7. 1,1-difluoroethane, commercially known as HFC 152a and having a molecular formula of C2H4F2 , is a refrigerant now used as a replacement for the many CFCs that are no longer allowed because they are so devastating to the ozone layer. Refrigerants generally work to cool things by absorbing energy and using that energy to evaporate. (The vapor is carefully contained, pumped to a remote location—like behind the refrigerator—and then the energy is released to metal coils that heat the air as the HFC 152a condenses back down to a liquid, where it is pumped back to the cooling chamber to start the cycle again.) The enthalpy of vaporization for HFC 152a is 20.4 kJ/mol. How many grams of HFC 152a are needed to cool 200.0 g of water from 50.0 °C to 40.0 °C? You will need the heat capacity of liquid water.
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