Consider the following chemical reaction between component A and B: A(?) + 2B(g) → C(g)+ 3D(l) …..ΔH°r = −2253.2 kJ i. State whether the reaction is exothermic or endothermic. ii. Based on the value of heat of reaction, explain the chemical reaction above in terms of the energy associated with breaking or formation of molecular bonds.
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.
Consider the following
A(?) + 2B(g) → C(g)+ 3D(l) …..ΔH°r = −2253.2 kJ
i. State whether the reaction is exothermic or endothermic.
ii. Based on the value of heat of reaction, explain the chemical reaction above in terms of the energy associated with breaking or formation of molecular bonds.
iii. Consider a similar reaction of A and B as the one shown above. However, the reaction now generates D in vapor form instead of liquid. Explain how the heat of reaction value differs from the one shown above.
iv. If the above reaction occurs in an isothermal system where there is no work interaction and both kinetic and potential energy changes are too small such that they are negligible, write the energy balance for the system.
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