Ammonia 1NH32 boils at -33 °C; at this temperature it has adensity of 0.81 g>cm3. The enthalpy of formation of NH31g2is -46.2 kJ>mol, and the enthalpy of vaporization of NH31l2is 23.2 kJ>mol. Calculate the enthalpy change when 1 L ofliquid NH3 is burned in air to give N21g2 and H2O1g2. Howdoes this compare with ΔH for the complete combustion of1 L of liquid methanol, CH3OH1l2? For CH3OH1l2, the densityat 25 °C is 0.792 g>cm3, and ΔHf° = -239 kJ>mol.
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.
Ammonia 1NH32 boils at -33 °C; at this temperature it has a
density of 0.81 g>cm3. The enthalpy of formation of NH31g2
is -46.2 kJ>mol, and the enthalpy of vaporization of NH31l2
is 23.2 kJ>mol. Calculate the enthalpy change when 1 L of
liquid NH3 is burned in air to give N21g2 and H2O1g2. How
does this compare with ΔH for the complete combustion of
1 L of liquid methanol, CH3OH1l2? For CH3OH1l2, the density
at 25 °C is 0.792 g>cm3, and ΔHf° = -239 kJ>mol.
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