Consider the following reaction which occurs at constant temperature and pressure: 2 HI(g) H2(g) + I2(g) H = 10.4 kJ Which has the higher enthalpy, 2 HI(g) or H2(g) + I2(g)? ___2 HI(g) ___H2(g) + I2(g) Without referring to tables indicate which of each of the pairs of choices below has the higher enthalpy: (a) ____1 mol of H2(g) and 1 mol of Cl2(g) at 25 oC ____2 mol of HCl(g) at 25 oC (b) ____2 mol of N2(g) at 300 oC ____1 mol of N2(g) at 300 oC
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 reaction which occurs at constant temperature and pressure:
| 2 HI(g) H2(g) + I2(g) | H = 10.4 kJ |
Which has the higher enthalpy, 2 HI(g) or H2(g) + I2(g)?
Without referring to tables indicate which of each of the pairs of choices below has the higher enthalpy:
(a)
(b)
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