4J.15

[Rachel Yoo 1F]

Which of the following compounds become less stable with respect to the elements as the temp is raised: (a) PCl5 (b) HCN (c) NO(g) (d)SO2?

[Sam Joslyn 1G]

To solve this you would have to calculate the change in Gibbs free energy of the formation of the compound (so for PCl5 you would have the reaction P + 5/2(Cl₂)-----> PCl5) then if delta G is negative it would be thermodynamically stable relative to its formation elements.

[Saachi_Kotia_4E]

this would depend on what you get for the entropy of reaction. PCl5 is less stable at higher temperatures because the resulting entropy is negative. HCN is more stable at higher temperature because the entropy is positive.