Given the standard enthalpy changes for the following two reactions: (1) 2C(s) + 2H₂(g) → C₂H4 (9) (2) 2C(s) + 3H₂(g) → C₂H6 (9) What is the standard enthalpy change for the following reaction? (3) C₂H4 (9) + H₂(g) → C₂H6 (9) AH° =? kJ Standard enthalpy change = AH = 52.3 kJ ΔΗ° = – 84.7 k. ==
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.
![Given the standard enthalpy changes for the following two reactions:
(1) 2C(s) + 2H₂(g) → C₂H4 (9)
(2) 2C(s) + 3H₂(g) → C₂H6 (9)
AH = 52.3 kJ
ΔΗ° = – 84.7 kJ
What is the standard enthalpy change for the following reaction?
(3) C₂H4 (9) + H₂(g) → C₂H6 (9)
AH° = ?
kJ
Standard enthalpy change =](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F2a948ce4-bfec-4c4b-a693-d4721e6497c9%2Fc4b82e4c-c839-4487-b6b5-0c0fd9a69182%2Fnccvnmc_processed.jpeg&w=3840&q=75)
![Please note that "geometry" refers to the molecular or ionic geometry.
:CI:
A. The Lewis diagram for CCI4 is: :CI-
:CI:
The electron-pair geometry around the C atom in CCl4 is
There are lone pair(s) around the central atom, so the geometry of CCl4 is
B. The Lewis diagram for CO₂ is:
o=c=o
Recall that for predicting geometry, double and triple bonds count as only one electron pair.
The electron-pair geometry around the C atom in CO₂ is
There are lone pair(s) around the central atom, so the geometry of CO₂ is](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F2a948ce4-bfec-4c4b-a693-d4721e6497c9%2Fc4b82e4c-c839-4487-b6b5-0c0fd9a69182%2Feyojvjx_processed.jpeg&w=3840&q=75)
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