## ice boc

Fdonovan 3D
Posts: 101
Joined: Sat Aug 17, 2019 12:16 am

### ice boc

Why do we use the ice box if the x is negligible when adding/subtracting? I'm confused why we use it if we end up taking the Xs out anyway.

Charysa Santos 4G
Posts: 107
Joined: Wed Sep 18, 2019 12:21 am

### Re: ice boc

You can only take out the X in the denominator if the K is less than 10^-3. The ice box helps to visualize and take inventory of what you start with and what is changing at the equilibrium.

Baoying Li 1B
Posts: 113
Joined: Sat Aug 17, 2019 12:18 am

### Re: ice boc

Using Ice box can help us organize our thoughts and avoid to make mistakes. I suggest to use it just in case or it may help you get some partial credit.

Daria MacAuslan 1H
Posts: 50
Joined: Sat Aug 17, 2019 12:16 am

### Re: ice boc

the ice box should pretty much always be used because it can help get rid of mistakes and organize our thoughts. x is only negligible when the k value is ver, very small. it has to be less than 1x10^-3 in order to just ignore x, otherwise you can't simply get rid of it.

Posts: 104
Joined: Fri Aug 09, 2019 12:16 am

### Re: ice boc

The X can only be taken out if it is very small and would not make a significant impact on the overall calculation, but this is usually only in either the numerator or denominator, rarely both. Therefore not all of the Xs can be considered negligible.

J_CHEN 4I
Posts: 54
Joined: Tue Nov 14, 2017 3:01 am

### Re: ice boc

Professor Lavalle gave a great analogy about approximations. Basically, let's you have 1,000,000 dollars and you subtract it by x amount. If x is very small, like 10 dollars, then x is negligible because 1,000,000 - 10 = 999,990, which is almost the same as 1,000,000. In acids and bases, a weak acid like acetic acid will not dissociate much in water, so the change in acetic acid (x) is negligible.

preyasikumar_2L
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

### Re: ice boc

The x is only negligible when adding/subtracting if the K value is very small (<10-3) or when the change in the concentrations/partial pressures is less than 5% of the original concentration/partial pressure. You will not always have a small K value, and the stoichiometric coefficients will not always be 1 which will sometimes make the changes in the concentrations/partial pressures be more than x (like 2x or 3x etc) and will require that value to be raised to a different power, so keeping everything in the ice box will allow you to keep track of everything and understand what goes where in the equation, and what value(s) you are solving for.

Gabriel Ordonez 2K
Posts: 113
Joined: Sat Jul 20, 2019 12:15 am

### Re: ice boc

The box is a visual aspect that allows us to work towards creating the equilibrium constant easily.