TPR: "Spontaneous" == Positive Keq? What?

[justadream]

TPR SW page 372 #7

“Given that the combustion of methane in oxygen is very spontaneous, at equilibrium the Keq for this reaction must be___?”



Answer: Positive and greater than 1.



How do you know it must be greater than 1? For example, diamond to graphite is very spontaneous but I’m pretty sure that Keq for that is <1.

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[Cawolf]

Actually graphite to diamond is spontaneous and has a Keq >1. It just is very slow and requires large temperature and pressure.

I thought all spontaneous reactions had a Keq >1?

 

[justadream]

@Cawolf

See TBR GC Book II page 137 Example 8.3

TBR GC Book II page 137 Example 8.3

“A reaction that is spontaneous in the forward direction corresponds with which of the following features??

Correct: It has a ratio of Q(of reaction) to Keq that is less than 1.

Incorrect: It has an equilibrium constant that is greater than 1.0.

TBR says "Favorability in the forward direction implies there is an excess of reactants and a shortage of products relative to equilibrium. This tell us nothing about the value of the equilibrium constant. The value of Keq may or may not be greater than 1.0"





(also posted in the thread below)


http://forums.studentdoctor.net/threads/tbr-deltag-and-k-relationship.1089206/

 

[justadream]

Came across another question today that seems to contradict the OP.

TPR SW page 388 #4

“What is the expected sign of deltaG and the expected value of the equilibrium constant, K, for the reactions associated with Experiment 2 [which is spontaneous]”?

Answer: deltaG is negative and K >1