Entropy Video Lessons

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# Problem: One of the major sources of NOx compounds in our atmosphere is the reaction between nitrogen and oxygen, for example N2(g) + 2O2(g) → 2NO2(g) This reaction is not favored at normal surface temperatures, but it does occur within internal combustion engines when air is mixed with the fuel to provide oxygen for the combustion reaction.    a. Before doing any calculations, predict the sign of ΔS°. ___________________.  Explain your reasoning.   b. Now calculate ΔH° and ΔS° for the above reaction. Some thermodynamic data is provided in the table below.   c. Is there a temperature range at which the above reaction would be spontaneous? If so, give the temperature range. If not, speculate on why the reaction occurs at higher temperatures.

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###### Problem Details

One of the major sources of NOx compounds in our atmosphere is the reaction between nitrogen and oxygen, for example

N2(g) + 2O2(g) → 2NO2(g)

This reaction is not favored at normal surface temperatures, but it does occur within internal combustion engines when air is mixed with the fuel to provide oxygen for the combustion reaction.

a. Before doing any calculations, predict the sign of ΔS°. ___________________.

b. Now calculate ΔH° and ΔS° for the above reaction. Some thermodynamic data is provided in the table below.

c. Is there a temperature range at which the above reaction would be spontaneous? If so, give the temperature range. If not, speculate on why the reaction occurs at higher temperatures.