Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: !!! on February 13, 2008, 10:37:13 PM

Title: Determining the Initial Equilibrium Concentration
Post by: !!! on February 13, 2008, 10:37:13 PM
(http://img81.imageshack.us/img81/5047/equilprobtu0.png)
The correct answer is 0.255 M, but I don't know how get to there.
The ICE stands for Initial concentration, Change in concentration, and Concentration at Equilibrium.
Help, please? And thank you!
Title: Re: Determining the Initial Equilibrium Concentration
Post by: Sev on February 13, 2008, 11:54:55 PM
Hi,

At the step: 4.56*10-3/[(n-0.228)2] = 6.3, just rearrange to: 4.56*10-3/6.3 = (n-0.228)2].

sqrt both sides: n-0.228 = 0.0269, and solve for n  :)
Title: Re: Determining the Initial Equilibrium Concentration
Post by: Yggdrasil on February 14, 2008, 12:02:06 AM
Your set up is correct, you just made a small error in the calculations.

When you square root both sides of the equation then multiply by (n-0.228) the RHS of the resulting equation should be 2.51n - 0.572 since Sqrt[6.30]*0.228 = 0.572.

[edit: Sev got to it first]
Title: Re: Determining the Initial Equilibrium Concentration
Post by: !!! on February 14, 2008, 01:05:19 AM
Oh, dear. I can't believe I overlooked that mistake.
Thank you very much, guys.