Van't Hoff Equation

[Carolina Gomez 2G]

When solving for the K constant at a different temperature assuming the standard entropy and standard enthalpy are constant, what are the steps we take to solve the equation ln K2/K1 = - (deltaH / R) [1/T2 - 1/T1]?

[StephanieIb]

I think all you need to do is plug in the given K, final and inital temperatures, and delta H from the problem to find the other K!

[Isabelle Hales 1J]

Hi! I believe you can plug in the two temperatures into T1 and T2. Then, if you know what one of the K values is, you can use it to find the other one. Hope this helps, and correct me if I'm wrong.

[Simrah_Ahmed1J]

So basically you are finding K₂ and already have all the other values:
1. solve right side of equation: ln K₂/K₁ = - (ΔH^o/R)[1/T₂ - 1/T₁]
now you have: ln K₂/K₁ = x
2. raise whatever you got on the right side of the equation to e to get rid of the natural log
now you have: K₂/K₁ = e^x
3. since you have the equilibrium value of K₁, you can multiply it to get rid of it on the left side so you can be left just K₂ to get your answer
now you've solved for your answer: K₂ = e^x * K₁

[David Chibukhchian 2G]

I definitely agree with the other answers and would add that it's important to use an R value of 0.0083145 instead of 8.3145. This is because the value of enthalpy, delta H naught, is given in kilojoules. Thus, we have to take this into account and use the appropriate R value; it was something that was confusing me at first because I didn't know what I was doing wrong. However, this made me realize what I was messing up. I hope that helps!

[BoparaiAdeshsurjit2F]

You would plug in all the stuff that is given and solve for the value needed

[Kayle Lim 2C]

There are many ways to manipulate the equation in order to solve it, so the way in which you solve for specific variables is up to you! There are really good examples mentioned above and I would also like to remind you that using the correct R value is super important and crucial!! Using the correct R value relates to which units are being used in the equation. Given all the constants, you would just need to plug them into the variables they correlate with and do some algebra to solve for what you are looking for. I really liked the steps provided by Simrah, that's exactly how I would have solved it.