A student carefully drops a 9.0g solid Zn pellet initially at 50.0°C into an insulated cup containing 30.0g of water at 27.8°C. The student predicts that the temperature of the water will increase after the pellet is added. Which of the following statements is the best justification for the student’s prediction? a. The metallic bonds between Zn atoms will break when the Zn is exposed to the water molecules, releasing energy that will be absorbed by the water molecules. b. Collisions between the water molecules and the surface of the Zn pellet will result in the transfer of energy, increasing the average kinetic energy of the water molecules. c. The strength of the hydrogen bonds between the water molecules will increase when the Zn pellet is added, decreasing the average kinetic energy of the water molecules. d. Collisions between Zn atoms in the solid will increase in frequency when the Zn is exposed to the water molecules, resulting in the transfer of energy to the surroundings
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.
A student carefully drops a 9.0g solid Zn pellet initially at 50.0°C into an
insulated cup containing 30.0g of water at 27.8°C. The student predicts that the temperature of the water will increase after the pellet is added. Which of the following statements is the best justification for the student’s prediction?
a. The metallic bonds between Zn atoms will break when the Zn is exposed to the water molecules, releasing energy that will be absorbed by the water molecules.
b. Collisions between the water molecules and the surface of the Zn pellet will result in the transfer of energy, increasing the average kinetic energy of the water molecules.
c. The strength of the hydrogen bonds between the water molecules will
increase when the Zn pellet is added, decreasing the average kinetic
energy of the water molecules.
d. Collisions between Zn atoms in the solid will increase in frequency
when the Zn is exposed to the water molecules, resulting in the transfer of energy to the surroundings
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