1) Which of the following processes is endothermic? a) melting of ice at 0oC b) the reaction of methane and oxygen c) cooling liquid water from 25oC to 0oC
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.
1) Which of the following processes is endothermic?
a) melting of ice at 0oC
b) the reaction of methane and oxygen
c) cooling liquid water from 25oC to 0oC
2) Which of the following processes requires the largest input of energy?
a) warming 1.0 g Fe by 10.oC (SpH of Fe = 0.449 J/goC)
b) warming 2.0 g Cu by 10.oC (SpH of Cu = 0.385 J/goC)
c) warming 4.0 g Pb by 10.oC (SpH of Pb = 0.127 J/goC)
d) warming 3.0 g Ag by 10.oC (SpH of Ag = 0.236 J/goC)
3) Which of the following processes will lead to a decrease in the internal energy of a system?
1- energy is transferred as heat into a system
2- energy is transferred as heat from the system
3- energy is transferred as work done on the system
4- energy is transferred as work done by the system
a) 1 and 3
b) 2 and 4
c) 1 and 4
d) 2 and 3
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