When HCl(aq) and NaOH(aq) are mixed in a beaker, the beaker feels warm to the touch. What is known about the enthalpy of this reaction? The reaction is exothermic. ΔH is positive. The reaction is endothermic. Heat is absorbed from the surroundings.
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.
1) When HCl(aq) and NaOH(aq) are mixed in a beaker, the beaker feels warm to the touch. What is known about the enthalpy of this reaction?
- The reaction is exothermic.
- ΔH is positive.
- The reaction is endothermic.
- Heat is absorbed from the surroundings.
2) Consider this combination reaction:
2Mg(s)+O2(g)→2MgO(s) ΔH=−1204 kJ
What is the enthalpy for the decomposition of 1 mole of MgO(s) into Mg(s) and O2(g)?
- -602 kJ/mol
- 602 kJ/mol
- -1204 kJ/mol
- 1204 kJ/mol
3) The enthalpy for the formation of 1 mole of NH3(aq) is -80.29 kJ/mol. What is the enthapy for the formation of 3 moles of NH3(aq)?
- -240.87 kJ
- −518×103 kJ
- -26.76 kJ
- -83.29 kJ
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