Dry ice is solid carbon dioxide. Instead of melting, solid carbondioxide sublimes according to the equation:CO2(s) ------------>CO2(g) When dry ice is added to warm water, heat from the water causesthe dry ice to sublime more quickly. The evaporating carbon dioxide produces a dense fog often used to create special effects. In a simple dry ice fog machine, dry ice is added to warm water in a Styrofoam cooler. The dryice produces fog until it evaporates away, or until the water gets too cold to sublime the dry ice quickly enough. A small Styrofoam cooler holds15.0 L of water heated to 85°C. Use standard enthalpies of formation to calculate the change in enthalpy for dry ice sublimation, and calculate themass of dry ice that should be added to the water so that the dry ice completely sublimes away when the water reaches 25 °C. Assume no heat loss to the surroundings. (The ∆H°f for CO2(s) is -427.4 kJ/mol.)
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.
Dry ice is solid carbon dioxide. Instead of melting, solid carbon
dioxide sublimes according to the equation:
CO2(s) ------------>CO2(g)
When dry ice is added to warm water, heat from the water causesthe dry ice to sublime more quickly. The evaporating carbon dioxide produces a dense fog often used to create special effects. In a simple dry ice fog machine, dry ice is added to warm water in a Styrofoam cooler. The dry
ice produces fog until it evaporates away, or until the water gets too cold to sublime the dry ice quickly enough. A small Styrofoam cooler holds
15.0 L of water heated to 85°C. Use standard enthalpies of formation to calculate the change in enthalpy for dry ice sublimation, and calculate the
mass of dry ice that should be added to the water so that the dry ice completely sublimes away when the water reaches 25 °C. Assume no heat loss to the surroundings. (The ∆H°f for CO2(s) is -427.4 kJ/mol.)
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