(4 blanks) An ice-making machine operates in a Carnot cycle. It takes heat from water at 0.0 °C and rejects heat to a room at 24.0 °C. Suppose that 85.0 kg of water at 0.0 °C are converted to ice at 0.0 °C. How much energy (in Joules) must be supplied to the machine to achieve this task? Sol. Since the machine is a operating in a Carnot cycle, then, its efficiency is e = TH| By virtue of first law, the work done to convert water to ice is given by W = Q = Thus, the total energy needed to convert 85 kg of water is ET = 687.5 J
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.
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