At which temperature will the following reactions reverse? Use the thermodynamic date provided at the end of the book.

Question

At which temperature will the following reactions reverse? Use the thermodynamic date provided at the end of the book.

a) 2Ca(s) + O2(g) -> 2CaO(s)
b) 2CH4(g) + 4 O2(g) -> 2CO2(g) + 4H2O(g)

Answer 1

Delta G = delta H - T*delta S.

You can look up delta Ho and delta So in your text. As long as delta G is negative the reaction is spontaneous OR if delta G is positive the reaction is not spontaneous but would be in the other direction. So set delta G = 0 and solve for T (in kelvin) and that will give you the T needed to just reverse the direction.