Chemistry--Dynamic Equilibrium?

Question

Please help me figure out this homework question:

"At 800 degrees C, the equilibrium constant for the reaction CO2 + H2 <--> CO + H20 is .279. At a different temperature the equilibrium constant is 0.100. Is this different temperature higher or lower than 800 degrees? Give your reasoning."

Thank you!

Answer 1

Hey,

Your equilibrium constants can tell you a lot... let's compare:

Firstly, they are both less than 1, meaning that in the equilibrium expression (the ratio of products over reactants), there are more reactants than products. This means that the reaction is reactant favoured. Make sense?

Look at the first K value (0.279), the reaction didn't get too far. You have another K value (0.100), it is lower. What does that tell you about the progress of the reaction? (at which temperature are there more reactants? more products?) This tells you which direction the equilibrium has to shift (from having 'more' of one (products or reactants) to having 'more' of the other (reactants or products) at the new temperature)

Do you know if the reaction is endothermic or exothermic? Can you guess? Or look it up? (If you know about Hess's Law, you can calculate the enthalpy, if not, don't worry about it) Now, treat 'heat' as if it were a chemical and put '+ heat' on one side of the equation: before the eq'm arrows if the reaction is endothermic, after the arrows if it's exothermic.

Now, pull it all together using LeChatelier's principle, you've figured out which direction the equilibrium has to shift by comparing the K values. Through the enthalpy, you know which side of the eq'm arrows the temperature (or heat) falls on.

Look at your desired equilibrium shift (from the K values), what would you have to do to the temperature to make that happen? (remember, treat it like a chemical...add heat or take it away and use LeChatelier, this will tell you what happens when you heat or cool the system.) That should tell you whether the second temperature is higher or lower than 800ºC.

I hope this helps...if it's all Greek...let me know and I'll take another stab at it ;)

Erin

Answer 2

at the different temperature, the K value has decreased

this means that you have less products and more reactants or that the reaction has shifted to the left

if the reaction is exothermic, raising the temperature will shift the reaction to the left (heat can be thought of as a product) and this means the second temperature is higher than the 800

if the reaction is endothermic, lowering the temperature will shift the reaction to the left (heat can be thought of as a reactant) and this means that the second temperature is lower than the 800

you can determine if the reaction is endothermic or exothermic by checking standard enthalpy values in your textbook - using those values, this reaction should be endothermic and lowering the temperature should shift the reaction to the left because K decreases - this means that the second temperature is less than 800 degrees

this seems like a bad question to me - you should have been told whether the reaction was endothermic or exothermic in the problem

Answer 3

dynamic = (replace) equilibrium = (fee are equivalent) dynamic equilibrium skill that the cost of leaving and stepping into are a similar... consequently, at any time... there is a similar quantity of stuff interior a gadget.. occasion: if a lecture room is crammed with one hundred human beings and each hour, 10 human beings pass away the ROOM.... yet coincidently, each and every hour... 10 human beings enters the ROOM on a similar time... after 20 hours... the room nevertheless has one hundred human beings... that's a Dynamic Equilibrium... besides the shown fact that they are changing, the gadget has a similar entity through comparable out-fee and in-fee