A student runs two experiments with a constant-volume "bomb" calorimeter containing 1300. g of water (see sketch at right). First, a 6.000 g tablet of benzoic acid (CH-CO₂H) 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 14.00 °C to 39.98 °C over a time of 14.9 minutes. Next, 5.570 g of acetylene (C₂H₂) are put into the "bomb" and similarly completely burned in an excess of oxygen. This time the temperature of the water rises from 14.00 °C to 60.18 °C. Use this information, and any other information you need from the ALEKS Data resource, to answer the questions below about this reaction: 2C₂H₂(g) + 50₂(g) → 4CO₂(g) + 2H₂O(g) - 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. O exothermic O endothermic O neither I stirrer kJ 0 thermometer chemical reaction 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. "bomb" A "bomb" calorimeter. water X insulation
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 student runs two experiments with a constant-volume "bomb" calorimeter containing
1300.g
First, a 6.000g
tablet of benzoic acid C6H5CO2H
is put into the "bomb" and burned completely in an excess of oxygen. (Benzoic acid is known to have a heat of combustion of /26.454kJg
.) The temperature of the water is observed to rise from 14.00°C
to 39.98°C
over a time of 14.9
minutes. Next, 5.570g
of acetylene C2H2
are put into the "bomb" and similarly completely burned in an excess of oxygen. This time the temperature of the water rises from 14.00°C
to 60.18°C
. Use this information, and any other information you need from the ALEKS Data resource, to answer the questions below about this reaction: |
|
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.
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