Consider the reaction. Al (s) + HCl (aq) → AlCl3 (s) + H2 (g) The following data were obtained for this reaction. Reactant/Products ∆H°f (kJ/mol) Al (s) 0.00 H2 (g) 0.00 HCl (aq) -167.2 AlCl3 (s) -704.2 A) Calculate ∆H°rxn in kJ. B) If 2.00 g of solid aluminum is mixed with 20.0 mL of 0.100 M hydrochloric acid in a coffee- cup calorimeter at constant pressure. The final volume of the solution was measured to be 22.5 mL and the density of the solution is 1.02 g/mL. The temperature of the calorimeter rises from 22.34 °C to 29.65 °C. The specific heat capacity of the solution is 4.20 J/(g°C). Calculate ∆H of the reaction in kJ/mol for this reaction. C) In addition, if the calorimeter is receiving an additional 3.98 kJ of work from the above reaction. Calculate ∆E of the reaction in kJ/mol for this reaction.
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 reaction.
Al (s) + HCl (aq) → AlCl3 (s) + H2 (g)
The following data were obtained for this reaction.
|
Reactant/Products |
∆H°f (kJ/mol) |
|
Al (s) |
0.00 |
|
H2 (g) |
0.00 |
|
HCl (aq) |
-167.2 |
|
AlCl3 (s) |
-704.2 |
A)
Calculate ∆H°rxn in kJ.
B)
If 2.00 g of solid aluminum is mixed with 20.0 mL of 0.100 M hydrochloric acid in a coffee- cup calorimeter at constant pressure. The final volume of the solution was measured to be 22.5 mL and the density of the solution is 1.02 g/mL. The temperature of the calorimeter rises from 22.34 °C to 29.65 °C. The specific heat capacity of the solution is 4.20 J/(g°C). Calculate ∆H of the reaction in kJ/mol for this reaction.
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