A student runs two experiments with a constant-volume "bomb" calorimeter containing 1500. g of water (see sketch at right). First, a 6.500 g tablet of benzoic acid (CH₂CO₂H) is put into the "bomb" and burned completely in an excess of oxygen. (Benzoic acid is known to have a heat of combustion of 26.454 kJ/g.) The temperature of the water is observed to rise from 18.00 °C to 44.66 °C over a time of 14.6 minutes. Next, 4.910 g of ethanol (C₂H5OH) are put into the "bomb" and similarly completely burned in an excess of oxygen. This time the temperature of the water rises from 18.00 °C to 40.44 °C. Use this information, and any other information you need from the ALEKS Data resource, to answer the questions below about this reaction: Is this reaction exothermic, endothermic, or neither? If you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in the second experiment. Calculate the reaction enthalpy AHxn per mole of H₂O. O exothermic O endothermic O neither C₂H₂OH(1) + 30₂(g) → 2CO₂(g) + 3 H₂O(g) Be sure any of your answers that are calculated from measured data are rounded to the correct number of significant digits. Note for advanced students: it's possible the student did not do these experiments sufficiently carefully, and the values you calculate may not exactly match published values for this reaction. kJ 0 kJ stirrer mol 0 thermometer chemical reaction "bomb" A "bomb" calorimeter. water X insulation S olo Ar
A student runs two experiments with a constant-volume "bomb" calorimeter containing 1500. g of water (see sketch at right). First, a 6.500 g tablet of benzoic acid (CH₂CO₂H) is put into the "bomb" and burned completely in an excess of oxygen. (Benzoic acid is known to have a heat of combustion of 26.454 kJ/g.) The temperature of the water is observed to rise from 18.00 °C to 44.66 °C over a time of 14.6 minutes. Next, 4.910 g of ethanol (C₂H5OH) are put into the "bomb" and similarly completely burned in an excess of oxygen. This time the temperature of the water rises from 18.00 °C to 40.44 °C. Use this information, and any other information you need from the ALEKS Data resource, to answer the questions below about this reaction: Is this reaction exothermic, endothermic, or neither? If you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in the second experiment. Calculate the reaction enthalpy AHxn per mole of H₂O. O exothermic O endothermic O neither C₂H₂OH(1) + 30₂(g) → 2CO₂(g) + 3 H₂O(g) Be sure any of your answers that are calculated from measured data are rounded to the correct number of significant digits. Note for advanced students: it's possible the student did not do these experiments sufficiently carefully, and the values you calculate may not exactly match published values for this reaction. kJ 0 kJ stirrer mol 0 thermometer chemical reaction "bomb" A "bomb" calorimeter. water X insulation S olo Ar
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter6: Thermochemistry
Section: Chapter Questions
Problem 83E: Give the definition of the standard enthalpy of formation for a substance. Write separate reactions...
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Concept explainers
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.
Question
Transcribed Image Text:A student runs two experiments with a constant-volume "bomb" calorimeter containing 1500. g of water (see sketch at
right).
First, a 6.500 g tablet of benzoic acid (CH₂CO₂H) is put into the "bomb" and burned completely in an excess of
oxygen. (Benzoic acid is known to have a heat of combustion of 26.454 kJ/g.) The temperature of the water is
observed to rise from 18.00 °C to 44.66 °C over a time of 14.6 minutes.
Next, 4.910 g of ethanol (C₂H5OH) are put into the "bomb" and similarly completely burned in an excess of oxygen.
This time the temperature of the water rises from 18.00 °C to 40.44 °C.
Use this information, and any other information you need from the ALEKS Data resource, to answer the questions
below about this reaction:
Is this reaction exothermic, endothermic, or neither?
If you said the reaction was exothermic or endothermic, calculate the amount of heat that was
released or absorbed by the reaction in the second experiment.
Calculate the reaction enthalpy AHxn per mole of H₂O.
O exothermic
O endothermic
O neither
C₂H₂OH(1) + 30₂(g) → 2CO₂(g) + 3 H₂O(g)
Be sure any of your answers that are calculated from measured data are rounded to the correct number of significant digits.
Note for advanced students: it's possible the student did not do these experiments sufficiently carefully, and the values you calculate may not exactly match
published values for this reaction.
kJ
0
kJ
stirrer
mol
0
thermometer
chemical reaction
"bomb"
A "bomb" calorimeter.
water
X
insulation
S
olo
Ar
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