Consider the combustion of liquid C₅H₈ in oxygen gas to produce carbon dioxide gas and water vapor. In an experiment, 0.1063 g of C₅H₈ is combusted to produce enough heat to raise the temperature of 150.0 g of water by 7.630 °C. a. Write the reaction that takes place using whole number coefficients. b. How many moles of C₅H₈ were burned? c. What quantity of heat, in
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. Consider the combustion of liquid C₅H₈ in oxygen gas to produce carbon dioxide gas and water vapor. In an experiment, 0.1063 g of C₅H₈ is combusted to produce enough heat to raise the temperature of 150.0 g of water by 7.630 °C.
a. Write the reaction that takes place using whole number coefficients.
b. How many moles of C₅H₈ were burned?
c. What quantity of heat, in J, was absorbed by the water assuming the specific heat of the water is 4.184 J/g*°C?
d. Then what quantity of that heat, in J, was produced by the combustion of C₅H₈? (include the appropriate sign)
e. What is the enthalpy change (in kJ/mol) for the combustion of C₅H₈?
f. Using the table below and the balanced chemical equation, determine the enthalpy of formation for C₅H₈, in kJ/mol?
g. If the literature value for the enthalpy of formation of C₅H₈ is 144 kJ/mol, then what is the magnitude of the percent error for this experiment?
2. The green light emitted by a stoplight has a wavelength of 505 nm. What is the frequency of this photon? (c = 3.00 × 10⁸ m/s).
3. A photon of blue light has a frequency of 7.50 × 10¹⁴ Hz. Calculate the wavelength of this photon (c = 3.00 × 10⁸ m/s) in nanometers.
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