# Chemical Forums

## Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: the rael walter white on September 12, 2021, 01:15:39 AM

Title: Problem with the ICE TABLE
Post by: the rael walter white on September 12, 2021, 01:15:39 AM
For the reaction 2HI -> H2 + I2 (all gas phase) the value of the equilibrium constant at 700K is 0.0183. If 3.0 moles of HI are placed in a 5-liter vessel and allowed to decompose according to the above equation, what percentage of the original HI would remain at equilibrium

Can someone explain why the equilibrium concentration constant for 2HI IS .6-X AND NOT .6-2X when filling out the ice table
Title: Re: Problem with the ICE TABLE
Post by: Borek on September 12, 2021, 03:00:24 AM
Can you show complete ICE table for this problem? A lot depends on what x refers to.
Title: Re: Problem with the ICE TABLE
Post by: Orcio_87 on September 12, 2021, 07:29:39 AM
Initial concentration of HI is 0,6 mol / liter, so final concentrations of HI, H2 and I2 are 0,6 - x, 1/2 x and 1/2 x (two molecules of HI produces only one H2 and one I2).
Title: Re: Problem with the ICE TABLE
Post by: Borek on September 12, 2021, 08:31:04 AM
Initial concentration of HI is 0,6 mol / liter, so final concentrations of HI, H2 and I2 are 0,6 - x, 1/2 x and 1/2 x (two molecules of HI produces only one H2 and one I2).

Or 0.6-2x, x and x, depending on what the x is. Both approaches are OK, it is just about knowing which one you use and what you solve for.
Title: Re: Problem with the ICE TABLE
Post by: the rael walter white on September 12, 2021, 06:13:05 PM
I totally agree but the solution we were given below confuses the heck out of me
Title: Re: Problem with the ICE TABLE
Post by: the rael walter white on September 12, 2021, 06:14:33 PM
Do you guys think this guy is right or am I just completely lost
Title: Re: Problem with the ICE TABLE
Post by: Borek on September 13, 2021, 03:20:27 AM
Do you guys think this guy is right or am I just completely lost

No, this solution is incorrect and you are perfectly right being confused. Stoichiometric coefficient of 2 is missing (either as just "2" or as "1/2").