The following combustion reaction was carried out using 3.88 g O2 and excess CH4. CH4 + 2O2 → CO2 + 2H2O. After the reaction was complete, the value of qsurr was determined from temperature measurements made in the surroundings. It was found that qsurr = +53.5 kJ. a. What is the value of qrxn? (This means the same as qsys.) b. Calculate the moles of reaction that was present in this experimental run. c. Divide the qrxn by the moles of reaction to determine ∆rH. Pay careful attention to the sign, units, and sig figs of your answer.
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.
The
following combustion reaction was carried out using 3.88 g O2 and excess CH4.
CH4 + 2O2 → CO2 + 2H2O.
After the reaction was complete, the value of qsurr was determined from temperature measurements made in the surroundings. It was found that qsurr = +53.5 kJ.
a. What is the value of qrxn? (This means the same as qsys.)
b. Calculate the moles of reaction that was present in this experimental run.
c. Divide the qrxn by the moles of reaction to determine ∆rH. Pay careful attention to
the sign, units, and sig figs of your answer.
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