The energy lost or gained by a chemical reaction is measured by the reaction's enthalpy change. The enthalpy change, AH,zn. for reactions that occur at constant pressure is the heat change of that process,q. Therefore, AH,n = 9p. Open container systems are constant pressure systems, so this is a reasonable assumption to make. Part C - You are provided the AH; of water in the table to the left. What is the standard enthalpy change (AHPzn) in kJ for the reaction below? 2H,(g) + 02 (g) - 2H,01) Enthalpy changes for a reaction AHzn can be estimated with the following equation: AHrn -En AH, (producta) -E m AH, (reactants) HA where n and m are the coefficients in the balanced chemical equation. The equation is read as "The sum of the molar enthalples of formation of tne products muitipiled by their coemclents minus the sum of the molar enthajpies of formation of the reactants multipiled by their coefficients." 497 kJ Standard Submit Previous Answers Request Answer Enthalpy of Substance Formation X Incorrect; Try Again AH°; (kJ/mol) H,0 (g) H,0 (1) -241.82 Part D- Use the table values and equation provided to calculate the enthalpy change (AHn) in kJ for the reaction below. -285.83 H2 (g) C (s, graphite) C (s, diamond) O (g) 02 (g) 0, (g) CO2 (g) Ca (s) CaO (s) CaCo, (s) Calcium carbonate will decompose to carbon dioxide and calcium oxide when heated to 840°C. CaCO: (s) = CaO(s) +CO2 (8) 1.88 HA 247.5 1.78 kJ 142.3 -393.5 Submit Previous Answers Request Answer -635.5 X Incorrect; Try Again -1207.1
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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