Mixing 10.0 g of CaC2 and 25.0 mL of H2O (ρ = 0.997044 g/mL) conforms to the thermochemical equation below: CaC2(s) + 2 H2O(l) ➜ Ca(OH)2(s) + C2H2(g) ΔH° = –127.2 kJ Molar masses: CaC2: 64.100 g/mol H2O: 18.015 g/mol Ca(OH)2: 74.092 g/mol C2H2: 26.038 g/mol A. Which statement applies? · 51.3 g Ca(OH)2 is formed. · 4.06 g C2H2 is formed. · H2O is the limiting reagent. · 1.81 g CaC2 remains. B. Determine the amount of heat involved. · –19.8 kJ · –88.0 kJ · 19.8 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.
Mixing 10.0 g of CaC2 and 25.0 mL of H2O (ρ = 0.997044 g/mL) conforms to the thermochemical equation below:
CaC2(s) + 2 H2O(l) ➜ Ca(OH)2(s) + C2H2(g) ΔH° = –127.2 kJ
Molar masses:
CaC2: 64.100 g/mol
H2O: 18.015 g/mol
Ca(OH)2: 74.092 g/mol
C2H2: 26.038 g/mol
A. Which statement applies?
· 51.3 g Ca(OH)2 is formed.
· 4.06 g C2H2 is formed.
· H2O is the limiting reagent.
· 1.81 g CaC2 remains.
B. Determine the amount of heat involved.
· –19.8 kJ
· –88.0 kJ
· 19.8 kJ
· 88.0 kJ
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