A hot 122.8 g lump of an unknown substance initially at 154.8 °C is placed in 35.0 mL of water initially at 25.0 °C and the system is allowed to reach thermal equilibrium. The final temperature of the system is 56.9 °C. Using this information and the specific heat values for several metals in the table, identify the unknown substance. Assume no heat is lost to the surroundings. graphite zinc aluminum titanium tungsten rhodium Substance Specific heat (J/(g•°C)) aluminum 0.897 graphite 0.709 rhodium 0.243 titanium 0.523 0.132 0.388 4.184 tungsten zinc 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.
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