In the late eighteenth century Priestley prepared ammonia by reacting HNO3(g) with hydrogen gas. The thermodynamic equation for the reaction is HNO3(g) + 4H2(g) → NH3(g) + 3H2O(g) ΔH = –637 kJ Calculate the amount of energy released when one mole of hydrogen gas reacts. Consider this to be a positive value. ________________ kJ b How much energy is released when 15.00 g of NH3(g) is made to react with an excess of steam to form HNO3 and H2 gases? Again, enter this as a positive value. HNO3(g) + 4H2(g) → NH3(g) + 3H2O(g) ΔH = –637 kJ _________________ kJ
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.
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In the late eighteenth century Priestley prepared ammonia by reacting HNO3(g) with hydrogen gas. The HNO3(g) + 4H2(g) → NH3(g) + 3H2O(g) ΔH = –637 kJ
Calculate the amount of energy released when one mole of hydrogen gas reacts. Consider this to be a positive value. ________________ kJ |
| b |
How much energy is released when 15.00 g of NH3(g) is made to react with an excess of steam to form HNO3 and H2 gases? Again, enter this as a positive value. HNO3(g) + 4H2(g) → NH3(g) + 3H2O(g) ΔH = –637 kJ
_________________ kJ |
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