Question

Physical Chemistry Question, I have no idea how to deal with this problem anyone that can help me? As far as his mention to class he solved a problem that was a lot easier than this and that is fairly useless in explaining how to deal with such a problem

Answer 1

have you tried setting both of the first equations equal to each other and solving for delta H knot

Answer 2

oh wait, i guess you don't know the stardard entropy either...

Answer 3

what about using the #1 equation, using T=450 K to find lnK then substitute that value in one of the other 2 equations?

Answer 4

have you tried anything?

Answer 5

I'm pretty sure that K is an equilibrium constant

Answer 6

that is in the equation, so I will end up with a quadratic formula for ln(K)

Answer 7

it is the equilibrium constant.. plug in 450 for T and T^2

you get a single value for K

Answer 8

if you solve the quadratic

Answer 9

https://www.wolframalpha.com/input/?i=ln%28x%29+%3D+-1.04+-+%281088x%29%2F%28450%29+%2B+%281.51%2810^5%29x^2%29%2F450^2

Answer 10

I get two values for K

Answer 11

I'm thinking that I should probably just omit the far right term and then solve for K

Answer 12

yeah i would say use the larger term

Answer 13

or you mean the 0.2 one

Answer 14

Why would you use the larger term?

Answer 15

lol why would you use the smaller term? i mean by looking at the reaction i would think it's decomposition to be larger for rate forward is probably larger

Answer 16

but then again i'm only speculating. i have thermodynamics next semester :S

Answer 17

I was just wondering what your reasoning behind using the larger rate constant was.

Answer 18

Ok I see what you are saying, I guess just use the larger rate constant, then just take the larger K value for 440K and 460K then use this equation to solve for the standard entropy

Answer 19

Sorry I mean standard enthalpy not entropy.

From there I can use the equation listed in the question to solve for standard entropy

Answer 20

Although this is all just guess on my part

Answer 21

yeah, that would probably work. yeah use the #2 one after

it makes sense to use van't hoffts but they probably gave you that 3rd equation for some reason. I just don't know how you could use it since it's the derivative

Answer 22

The equation I posted is derived from the 3rd equation I'm pretty sure. Oh yeah it is because it is because if you take the integral of both sides of the equation you will end up with it

Answer 23

I could be wrong though

Answer 24

Yeah it is just a differential equation

Answer 25

yeah i totally see what you mean, bringing the d(1/T) to the right side and integrating

Answer 26

do it up dude, i'm pretty sure you're right

Answer 27

I will probably do it soon, still finishing up other questions, hopefully I get reasonable values. I will post the solution I came to in a bit, thanks for helping me get started on this.

Answer 28

yeah, dude no problem. hopefully it works, is it an assigment for marks or practice?

Answer 29

practice assignment

Answer 30

nice