Chemical Equilibrium and Concentration

[Procrastinate]

The reaction between hydrogen and fluorine has an equilibrium constant of 1.15x10² at a certain temperature. Given the reaction equation H2(g) + F2(g) -> 2HF(g), calculate the equilibrium concentration of HF after 3.00 mol of each component is added to a 1.500 L flask.

I attempted solving it by calculating the concentration of H2 and F2 which were each 2 (3/1.5). Afterwards, I formed the equilibrium expression and multiplied 2 squared (for H2 and F2) with 1.15x10². Then I found the square root of the answer since HF would be raised to the power of 2 which was about 21. However, the answer is 1.5M and I don't know how they got that.

 

[Borek]

Hydrogen and fluorine react, so their equilibrium concentrations are different from the initial ones. ICE table?

 

[Procrastinate]

Hydrogen and fluorine react, so their equilibrium concentrations are different from the initial ones. ICE table?

Thanks. How do you know when to use an ICE table in a question?

 

[Borek]

Whenever it is obvious that I, C and E are nicely defined.

Just don't use ICE table for buffer questions.

 

[Procrastinate]

Whenever it is obvious that I, C and E are nicely defined.

Just don't use ICE table for buffer questions.

I tried an ICE table for a buffer solution once but it gives me the same answer as the Henderson-Hasselbalch equation anyways (which is quicker to plug in all the numbers.)

 

[Borek]

I never stated it is impossible to do buffer questions with ICE table, it just IMHO doesn't make sense.