A fully charged battery contains 0.02 kmol Ag₂O (silver oxide) and 0.02 kmol Zn (zinc). The battery is initially at a temperature of 21°C. The fully charged battery is then discharged for half an hour under adiabatic conditions (no heat leaves the system). During the half hour of being discharged, the electric current from the battery does 200 kJ of work external to the battery system (none of this external work heats the battery). During this half hour, 0.001 kmol of both reactants are consumed in the net cell discharge reaction: Please see the following table for heat capacities and heats of formation. The heats of formation below show the amount of energy (kJ) needed to form one kmole of each component. If the heat of formation is negative, then forming that species releases energy (to do work or provide heat). Therefore, to create one kmole of silver oxide 29000 kJ energy is released and is generated in the battery (for work or heat), and if one kmole of silver oxide decomposes into its constituents, 29000 kJ of energy is required and is consumed by the battery. Table 1. Heat of formation Ag₂0 + Zn→ 2Ag + Zn0 Component hᵒf (kJ/kmol) Ag₂O -29000 Zn 0 Ag 0 ZnO -348000

Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
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Chapter1: Introduction
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A fully charged battery contains 0.02 kmol Ag₂O (silver oxide) and 0.02 kmol Zn (zinc). The battery is
initially at a temperature of 21°C. The fully charged battery is then discharged for half an hour under
adiabatic conditions (no heat leaves the system). During the half hour of being discharged, the electric
current from the battery does 200 kJ of work external to the battery system (none of this external work
heats the battery). During this half hour, 0.001 kmol of both reactants are consumed in the net cell
discharge reaction:
Please see the following table for heat capacities and heats of formation.
The heats of formation below show the amount of energy (kJ) needed to form one kmole of each
component. If the heat of formation is negative, then forming that species releases energy (to do work
or provide heat). Therefore, to create one kmole of silver oxide 29000 kJ energy is released and is
generated in the battery (for work or heat), and if one kmole of silver oxide decomposes into its
constituents, 29000 kJ of energy is required and is consumed by the battery.
Table 1. Heat of formation
Ag₂0 + Zn → 2Ag + Zn0
Component
hᵒf (kJ/kmol)
Ag₂O
-29000
Zn
0
Ag
0
ZnO
-348000
Transcribed Image Text:A fully charged battery contains 0.02 kmol Ag₂O (silver oxide) and 0.02 kmol Zn (zinc). The battery is initially at a temperature of 21°C. The fully charged battery is then discharged for half an hour under adiabatic conditions (no heat leaves the system). During the half hour of being discharged, the electric current from the battery does 200 kJ of work external to the battery system (none of this external work heats the battery). During this half hour, 0.001 kmol of both reactants are consumed in the net cell discharge reaction: Please see the following table for heat capacities and heats of formation. The heats of formation below show the amount of energy (kJ) needed to form one kmole of each component. If the heat of formation is negative, then forming that species releases energy (to do work or provide heat). Therefore, to create one kmole of silver oxide 29000 kJ energy is released and is generated in the battery (for work or heat), and if one kmole of silver oxide decomposes into its constituents, 29000 kJ of energy is required and is consumed by the battery. Table 1. Heat of formation Ag₂0 + Zn → 2Ag + Zn0 Component hᵒf (kJ/kmol) Ag₂O -29000 Zn 0 Ag 0 ZnO -348000
Table 1. Heat of formation
Component
hᵒf (kJ/kmol)
Ag₂O
-29000
Component
C (kJ/(kmol. K))
Zn
0
Ag₂O
80
The table below shows the amount of energy (in kJ) needed to change the temperature of one kmole of
each species by one degree Kelvin. Positive heat energy increases temperatures and negative heat
energy decreases temperatures.
Table 2. Heat capacities
Ag
0
Zn
26
ZnO
-348000
Ag
26
ZnO
42
Calculate the internal temperature of the battery after the half hour of discharge. Your complete
solution should contain the following sections: Given, Find, Assumptions, Analysis, and Conclusions.
Transcribed Image Text:Table 1. Heat of formation Component hᵒf (kJ/kmol) Ag₂O -29000 Component C (kJ/(kmol. K)) Zn 0 Ag₂O 80 The table below shows the amount of energy (in kJ) needed to change the temperature of one kmole of each species by one degree Kelvin. Positive heat energy increases temperatures and negative heat energy decreases temperatures. Table 2. Heat capacities Ag 0 Zn 26 ZnO -348000 Ag 26 ZnO 42 Calculate the internal temperature of the battery after the half hour of discharge. Your complete solution should contain the following sections: Given, Find, Assumptions, Analysis, and Conclusions.
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