eqm constant (1 Viewer)

[lilchezza]

just studying for my 1/2 yrly on monday and wanted to make sure that by finding the eqm constant, using different concentrations, means we are determining whether the system is at eqm, and if the dif answers are close together, it is? Also, just wondering what the symbol actually is for eqm constant as in my examples i have KC and K, but on a previous thread someone explained it using Ka?

 

[Dreamerish*~]

Eqm = Equilibrium? I have no idea what your question is.

 

[Riviet]

Yep, she is referring to equlibrium, although I don't think this is in the syllabus. My teacher likes to go on about things outside of the course and this was one of the ideas he touched on.
[reactants] = k
[products]

When the two concentrations are close together, then k approaches 1, and I think this means that the reactant and products are close to equilibrium. Correct me if I'm wrong.

 

[lilchezza]

Yes, I was referring to equilibrium, sorry about the abbreviations. I’m glad I’m not the only one totally confused by this concept.
Basically, in my notes, I have;
For a chemical eqm to exist in a reaction mixture, the reaction quotient must be equal to the equilibrium constant.
Reaction quotient = (product)^2 over (reactant A)(Reactant B)
The eqm constant can always be predicted from a balanced chemical eqn.
dD+eE " fF+gG
Where lower case letters represent no of moles, and upper case letters represent concentrations of species.
If a system is at eqm then;
KC = (F)^f(G)^g over (D)^d(E)^e
Followed by an eg;
2HI"H2+I2 (sorry can’t do numbers at bottom)
so KC = (H2)(I2) over (HI)^2
so if
(HI) = 3.53x10^-3
(H2) = 0.48x10^-3
(I2) = 0.48x10^-3 then;
(0.48x10^-3)x(0.48x10^-3) over (3.66x10^-3)^2
KC= 0.0185
Followed by two other eg’s with close answers (0.0186 & 0.0183), so I think your last statement was correct.
If this isn’t in the syllabus, does that mean it can’t be in my test? I thought only things from the syllabus could be in it, but my teacher “hinted” to go over it, and she wrote the test, so basically I’M SCREWED

 

[Riviet]

If this isn’t in the syllabus, does that mean it can’t be in my test? I thought only things from the syllabus could be in it, but my teacher “hinted” to go over it, and she wrote the test, so basically I’M SCREWED

This is definitely not in the syllabus, although your teachers ARE allowed to put things that are related to the topics studied in an assessment or your half yearly exams. If your teacher has specifically told you or "hinted" that it will be in the exam or assessment, then I'm sorry, you are going to have to know about it. If you're still not sure, ASK him/her again if it is in the test. Good luck.