at high temperatures, ammonia decomposes to N2 and H2.

Question

2 NH3(g)--> N2 (g) + 3H2(g)

Delta H for the reaction is positive and delta S is positive.
Estimate the temperature at which this reaction becomes spontaneous

Answer 1

Use the tables in your text/notes to evaluate dHo for the rxn and dSo for the rxn and set those up as dGo = dHo - TdSo. Then set dGo = 0 and solve for T. That will be the point at which the rxn is spontaneous/non-spontaneous (or the reverse). dH often doesn't change much with T and dS often doesn't change much with T so this allows one to estimate (note that word in the problem) the change over point.

Answer 2

37

Answer 3

192