Among the equations below, indicate all those that are exothermic. i. HNO3(aq) + KOH(aq) → KNO3(aq) + H2O(l) ∆H = -53 kJ ii. Fe3O4(s) + CO(g) + 38 kJ → 3FeO(s) + CO2(g) iii. CaO(s) + H2O(l) → Ca(OH)2(aq) + 65.2 kJ iv. H2O2(l) → H2(g) + O2(g) ∆H = 188 kJ v. NaOH(s) + HCl(l) → NaCl(s) + H2O(l) ∆H = -178 kJ issue 14 Among the substances below, identify the one that will have a standard enthalpy of formation (∆Hf) equal to 0 kJ/mol. a) Al(s) b) CaCl2(s) c) MgCl2(l) d) KBr(s) issue 17 A sample of ethylene glycol, used in automobile radiators, has a mass of 33.7 g. This sample releases 781 J of heat. The initial temperature of the sample is 21.8°C. What is its final temperature?
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.
issue 13
Among the equations below, indicate all those that are exothermic.
i. HNO3(aq) + KOH(aq) → KNO3(aq) + H2O(l) ∆H = -53 kJ
ii. Fe3O4(s) + CO(g) + 38 kJ → 3FeO(s) + CO2(g)
iii. CaO(s) + H2O(l) → Ca(OH)2(aq) + 65.2 kJ
iv. H2O2(l) → H2(g) + O2(g) ∆H = 188 kJ
v. NaOH(s) + HCl(l) → NaCl(s) + H2O(l) ∆H = -178 kJ
issue 14
Among the substances below, identify the one that will have a standard enthalpy of formation (∆Hf) equal to 0 kJ/mol.
a) Al(s)
b) CaCl2(s)
c) MgCl2(l)
d) KBr(s)
issue 17
A sample of ethylene glycol, used in automobile radiators, has a mass of 33.7 g. This sample releases 781 J of heat. The initial temperature of the sample is 21.8°C. What is its final temperature?
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