first-aid hot packs, giving off heat when dissolved in water. A coffee-cup calorimeter at 25ºC contains 15.9 mL of water at 25ºC. A 1.00-g sample of is dissolved in the water and 0.755 kJ of heat is evolved. (You can make the following assumptions about the solution: volume = 15.9 mL, density = 1.00 g/mL, specific heat = 4.18 J/g · ºC.) What is qH2O? qH2O = _________ kJ
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.
Magnesium sulfate is often used in first-aid hot packs, giving off heat when dissolved in water. A coffee-cup calorimeter at 25ºC contains 15.9 mL of water at 25ºC. A 1.00-g sample of is dissolved in the water and 0.755 kJ of heat is evolved. (You can make the following assumptions about the solution: volume = 15.9 mL, density = 1.00 g/mL, specific heat = 4.18 J/g · ºC.)
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What is qH2O? qH2O = _________ kJ |
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