A chemical reaction is carried out in a calorimeter with the following heat capacity (C = 265.5 J/ºC). The reaction occurs in 30.4 g of water. The initial temperature before the reaction is 29.2 ºC and the final temperature after the reaction is 61.5 ºC. The temperature change is the same for the water as it is for the calorimeter. What is the energy change for the reaction (qrxn) in kJ? The qwater can be found using q=mCs∆T. The qcalorimeter can be found using q=C∆T. In this case, there are 3 energy changes that are happening (qcal, qwater, and qreaction). The sum of those 3 energy changes will be equal to zero. Be sure to be careful with the sign of each value.
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.
A
The qwater can be found using q=mCs∆T.
The qcalorimeter can be found using q=C∆T.
In this case, there are 3 energy changes that are happening (qcal, qwater, and qreaction). The sum of those 3 energy changes will be equal to zero. Be sure to be careful with the sign of each value.
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