What to do if Kc isn't given.

[Ellie Garcia 2L]

Hi all.

I'm attempting to do a problem where I'm given the molarity of both the reactions and products side. However, I'm never given a Kc in this problem. Is there a value that one would use in case the Kc isn't given or does the Kc always need to be explicitly stated? Any help would be greatly appreciated!

[Jonathan Kwon 2J]

Usually, Kc is given when trying solve these equilibrium problems and you should not try to have a place-holding number if Kc is not given. However, if Kc is not given, then the problem is probably asking for you to find Kc using the concentrations given.

[Chem_Mod]

Do you know which textbook problem this is?

[Ellie Garcia 2L]

Hi all.

The question I'm answering is:

When 0.70 mol NO2 was placed in a 1.00 L flask and allowed to reach equilibrium, it’s
concentration was found to be 0.28 M, once equilibrium was established. Calculate Kc for
this reaction.




a) 1.9
b) 0.94
c) 0.47
d) 0.14

I've set up an ICE table but it seems a bit of a hassle to solve since there isn't much I can do unless I'm looking at it incorrectly. If it helps, the correct answer ends up being c).