Question

I have a question about a Gibbs Free Energy Question that we are doing in my AP Biology Class...

The Hydrogenation of ethane gas under standerd conditions (Temp= 298.15 K) shows a decrease in disorder (DeltaS= -0.1207 kJ/(mol*K)) during an exothermic reaction (DeltaH = -136.9 kJ/mol). Determine whether the reaction is spontaneous or nonspontaneous by calculating Delta G.

I have
DeltaG= -136.9kJ/mol - 298.15K (-0.1207kJ/mol*K)

-136.9kJ/mol - - 35.99K

= -100.9

I don't know if this is correct and what the label would be. Please help :)

Answer 1

yeah, that's right.

It's spontaneous if \(\Delta G<0\) and non-spontaneous if \(\Delta G>0\)

Answer 2

Ok so what would the label for -100.9 be? or is there one?

Answer 3

If the value you get is less than zero, then it's spontaneous. If its more than 0 then it's non-spontaneous, and if zero it's at equilibrium.

Answer 4

Ok thanks,

So there isn't like kJ/mol or anything after the number? It's just -100.9 and spontaneous?
Sorry, my teacher really didn't explain this very well.

Answer 5

just cancel the units are you go along,

\(\Delta G= -136.9kJ/mol - 298.15\cancel K (-0.1207kJ/mol*\cancel K)\)

\(\Delta G-136.9kJ/mol + 35.99kJ/mol\)

\(\Delta G= -100.9~kJ/mol\)

Answer 6

Ok thank you :) That really helped

Answer 7

no problem!

Answer 8

glad it helped