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.
If 15.0 mL of a 1.5M HCl solution at 21.5°C is mixed with 25.0mL of a 1.5M NaOH solution at 21.5°C that is in a calorimeter, and the final mixed solution temperature rises to 28.5°C, what is the ΔHrxn for this process? Assume that Ccalorimeter = 35.5J/°C.
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Write the balanced equation (total ionic) for the reaction?
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What is the source of the heat that is causing the increase in temperature?
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Calculate the amount of heat absorbed or lost by the HCl/NaOH solution. Assume aqueous conditions. (Cwater = 4.18 J / g·K , d = 1.00 g/mL).
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Calculate the amount of heat absorbed or lost by the calorimeter.
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Determine the amount of heat absorbed or lost during this reaction (qrxn).
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Which of the reactants is the limiting reagent? Determine the moles of the limiting reagent.
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Determine the amount of heat given off per mole of limiting reagent (ΔHrxn). Make sure to include an appropriate sign indicating whether it is an endothermic (+) or exothermic (-) process. Provide your answer in units of kJ/mol.
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