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TBR GenChem thermodynamics Example 8.11
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I was reviewing this question when I saw something that confused me.
The H20 is listed as a gas, and the question is asking for the STANDARD enthalpy change. Therefore wouldn't we have to take into account the energy released from converting h20 (g) to (l) and use the h20 (l) Heat of formation? Since water is a liquid in standard conditions?
I'd appreciate clarification here, thanks.
The H20 is listed as a gas, and the question is asking for the STANDARD enthalpy change. Therefore wouldn't we have to take into account the energy released from converting h20 (g) to (l) and use the h20 (l) Heat of formation? Since water is a liquid in standard conditions?
I'd appreciate clarification here, thanks.
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There are standard enthalpies of formation for liquid water and water vapor. If you were trying to solve this using a thermodynamic cycle, then yes - the heat of condensation would need to be accounted for.
Generally though, this problem will have a table that provides the data and it is just important you use the right phase. Take a look at this table I found and note that water is on there for both phases.
http://nshs-science.net/chemistry/common/pdf/R-standard_enthalpy_of_formation.pdf
Generally though, this problem will have a table that provides the data and it is just important you use the right phase. Take a look at this table I found and note that water is on there for both phases.
http://nshs-science.net/chemistry/common/pdf/R-standard_enthalpy_of_formation.pdf
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Right, so they gave a table in the book for this with the appropriate gas and liquid standard enthalpies for water.
This has been bugging me but since they asked for the standard enthalpy for the reaction that means everything must be in its standard state, which means that when they calculated the reaction with the enthalpy of gaseous water, they were incorrect.
They gave a specific reaction where water was gaseous, which is throwing me off a bit. For the purposes of the MCAT when doing these kinds of problems we should automatically check to see everything is in its standard state, right?
This has been bugging me but since they asked for the standard enthalpy for the reaction that means everything must be in its standard state, which means that when they calculated the reaction with the enthalpy of gaseous water, they were incorrect.
They gave a specific reaction where water was gaseous, which is throwing me off a bit. For the purposes of the MCAT when doing these kinds of problems we should automatically check to see everything is in its standard state, right?
