Ms. Prohaska is trying to determine the enthalpy of combustion for propan-2-ol. She heats up a sample of water by burning the propan-2-ol in an alcohol burner, as represented below. The alcohol burner uses a wick to draw liquid up into the flame. The mass of the propan-2-ol combusted is determined by measuring the mass of the alcohol burner before and after combustion. -Water Wick -C₂H₂OH(1) -Water -C₂H₂OH(1) Initial Final When Ms. Prohaska does the same experiment for trial two, she uses the same mass of water and the same initial temperature of water. However, she uses an alcohol burner that contains propan-2-ol that is contaminated with water (which can dissolve in propan-2-ol). The different in mass before and after the combustion is the same as in trial one. Do you think the final temperature of the water in the beaker heated by the contaminated alcohol burner be greater than, less than, or equal to the final temperature of the water in the beaker in the first trial? Justify 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.
Ms. Prohaska is trying to determine the enthalpy of combustion for propan-2-ol. She heats up a sample
of water by burning the propan-2-ol in an alcohol burner, as represented below. The alcohol burner
uses a wick to draw liquid up into the flame. The mass of the propan-2-ol combusted is determined by
measuring the mass of the alcohol burner before and after combustion.
When Ms. Prohaska does the same experiment for trial two, she uses the same mass of water and the
same initial temperature of water. However, she uses an alcohol burner that contains propan-2-ol that
is contaminated with water (which can dissolve in propan-2-ol). The different in mass before and after
the combustion is the same as in trial one.
Do you think the final temperature of the water in the beaker heated by the contaminated alcohol
burner be greater than, less than, or equal to the final temperature of the water in the beaker in the
first trial? Justify your answer.
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