When determining the heat of vaporization (ΔHvap) of two compounds: ethanol and cyclohexane, the following data was found: The slope (K) for ethanol is -7892.7 The slope (K) for cyclohexane is -3346.2 Answer the following: 1.) How much energy in kilojoules (kJ) does it require to vaporize ethanol and cyclohexane? 2.) Which compound has a higher heat of vaporization? 3.) Why is the heat of vaporization different between ethanol and cyclohexane? 4.) Explain why one compound's heat of vaporization is higher than the other.
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.
When determining the heat of vaporization (ΔHvap) of two compounds: ethanol and cyclohexane, the following data was found:
The slope (K) for ethanol is -7892.7
The slope (K) for cyclohexane is -3346.2
Answer the following:
1.) How much energy in kilojoules (kJ) does it require to vaporize ethanol and cyclohexane?
2.) Which compound has a higher heat of vaporization?
3.) Why is the heat of vaporization different between ethanol and cyclohexane?
4.) Explain why one compound's heat of vaporization is higher than the other.
Extra Credit: When comparing methanol (CH3OH) to ethanol (C2H5OH), they have the same intermolecular forces (dispersion, dipole-dipole, and hydrogen bonding). However, methanol's boiling point is 64.7 ºC and ethanol's boiling point is 78.4 ºC. Can you explain why these two compounds with the same intermolecular forces have two different boiling points? Which compound do you expect to have a greater vapor pressure?
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