Use the following enthalpy data and apply Hess's Law to calculate the formation of NH4Cl(s). 1/2 N2(g) + 3/2 H2 (g) ---> NH3(g) .......................... -45.77 kJ/mol H2(g) + Cl(g) ---> 2HCl (g) ....................................... -184.62 kJ/mol NH3(g) ---> NH3(aq) ............................................... -35.40 kJ/mol HCl(g) ---> HCl(aq) ................................................... -72.84 kJ/mol NH3(aq) + HCl(aq) ---> NH4Cl(aq) ............................ 28.54 kJ/mol NH4Cl(s) ---> NH4Cl(aq) ......................................... -15.38 kJ/mol ΔH for NH4Cl(s): 1/2 N2(g) + 2 H2(g) + 1/2 Cl2(g) ---> NH4Cl(s)
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.
Use the following enthalpy data and apply Hess's Law to calculate the formation of NH4Cl(s).
1/2 N2(g) + 3/2 H2 (g) ---> NH3(g) .......................... -45.77 kJ/mol
H2(g) + Cl(g) ---> 2HCl (g) ....................................... -184.62 kJ/mol
NH3(g) ---> NH3(aq) ............................................... -35.40 kJ/mol
HCl(g) ---> HCl(aq) ................................................... -72.84 kJ/mol
NH3(aq) + HCl(aq) ---> NH4Cl(aq) ............................ 28.54 kJ/mol
NH4Cl(s) ---> NH4Cl(aq) ......................................... -15.38 kJ/mol
ΔH for NH4Cl(s): 1/2 N2(g) + 2 H2(g) + 1/2 Cl2(g) ---> NH4Cl(s)
The equation above is already balanced, I'm just really confused as to how I use Hess's Law to "add" the other enthalpy reactions to get to this one. Like, I don't know which ones to flip, where to multiple or anything. Any help would be greatly appreciated!
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