## ICE BOX

205150314
Posts: 106
Joined: Wed Feb 20, 2019 12:16 am

### ICE BOX

when do we know that X is too small to be making a difference for the denominator in the ICE box?

Hannah Pham
Posts: 104
Joined: Fri Aug 09, 2019 12:17 am

### Re: ICE BOX

You would X is too small when K < 10^3

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

### Re: ICE BOX

If your K is less than 10^-3, you can approximate the denominator.

Anna Heckler 2C
Posts: 102
Joined: Wed Sep 18, 2019 12:18 am

### Re: ICE BOX

If X is smaller than 10^-3, then the affect of subtracting this value from the denominator is negligible.

105311039
Posts: 107
Joined: Fri Aug 02, 2019 12:16 am

### Re: ICE BOX

when your K value is less than 10^-3 you can assume that it is too small to affect your concentration.

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

### Re: ICE BOX

If the Kc, Ka, or Kb is smaller than 10^-3, then you can assume to remove the -x because it is small relative to the other number.

Jesse Anderson-Ramirez 3I
Posts: 54
Joined: Thu Sep 26, 2019 12:18 am

### Re: ICE BOX

If any of the K values are smaller than 10^-3 then they are considered negligible.

Ashley Nguyen 2L
Posts: 103
Joined: Sat Aug 17, 2019 12:18 am
Been upvoted: 1 time

### Re: ICE BOX

If the x is < 10^-3, then you can assume that the x has no effect on the denominator.

Angus Wu_4G
Posts: 102
Joined: Fri Aug 02, 2019 12:15 am

### Re: ICE BOX

You can use the approximation if the K value is less than 1X10^-3. After you obtain your final H30+ concentration, you should also make sure the final H30+ concentration is less than 5% of the initial concentration of acid. If it is less than 5%, your approximation is probably fine. If your final concentration is greater than 5% of the initial acid, then your answer could be potentially off, depending on how many significant figures the problem has.

vanessas0123
Posts: 100
Joined: Wed Sep 11, 2019 12:17 am

### Re: ICE BOX

x is too small if it's < 10^-3.

Kishan Shah 2G
Posts: 132
Joined: Thu Jul 11, 2019 12:15 am

### Re: ICE BOX

yes, the cutoff is 10^-3.

However, I would advise only to use the short cut when the value is 10^-5 since you don't want to take a chance and have your answer be off by a few digits. On the test I would always check your answer using the quadratic formula if you used the short cut.

005384106
Posts: 101
Joined: Sat Aug 24, 2019 12:16 am

### Re: ICE BOX

If K is 10^-3 then do you assume that x can be represented as 0.

Jialun Chen 4F
Posts: 108
Joined: Sat Sep 07, 2019 12:16 am

### Re: ICE BOX

The cutoff is 10^-3. Yet in cases of weak acids and bases, one may want to check the % ionization to ensure the approximation is valid (i.e, the quadratic formula is still necessary if the final percentage is >5%).

Juana Abana 1G
Posts: 100
Joined: Wed Sep 18, 2019 12:15 am

### Re: ICE BOX

When the K value is less than 10^-3 then you can assume that the K value it is too small to affect the concentration.

Areli C 1L
Posts: 95
Joined: Wed Nov 14, 2018 12:19 am

### Re: ICE BOX

I would agree that 10^-3 would be the cut-off, but that margin is so close. 10^-4 or 10^-5 would be a safer option. If you do decide to neglect x at 10^-3 always check at the end if your answer is withing 5%.

Matthew ILG 1L
Posts: 112
Joined: Sat Aug 17, 2019 12:15 am

### Re: ICE BOX

I believe that Dr. Lavelle said we can ignore x when K<10^-3.

zfinn
Posts: 106
Joined: Fri Aug 30, 2019 12:16 am

### Re: ICE BOX

when x is <5% of the initial concentration you can omit it

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

### Re: ICE BOX

if the k is smaller than 10^3, then the x in the ice box can be disregarded in the denominator.

J Medina 2I
Posts: 102
Joined: Wed Sep 25, 2019 12:17 am

### Re: ICE BOX

If you exclude the x and want to double check afterwards to see if the approximation is accurate, then you can calculate the protonation percentage, or deprotonation percentage depending on the question, and if it is below 5% then the approximation is correct.

Owen-Koetters-4I
Posts: 50
Joined: Fri Sep 28, 2018 12:16 am

### Re: ICE BOX

x is small when its less than 10^-3 of initial concentration of acid or base

KHowe_1D
Posts: 103
Joined: Thu Jul 25, 2019 12:15 am
Been upvoted: 1 time

### Re: ICE BOX

X is too small when K<10^-3

AronCainBayot2K
Posts: 101
Joined: Fri Aug 30, 2019 12:17 am

### Re: ICE BOX

If the number (x) is less than 10^-3

Catherine Daye 1L
Posts: 104
Joined: Wed Sep 11, 2019 12:16 am

### Re: ICE BOX

When it’s smaller than 10^-3

Sean Tran 2K
Posts: 65
Joined: Sat Aug 17, 2019 12:17 am

### Re: ICE BOX

If X is less than 10^-3

Maria Poblete 2C
Posts: 102
Joined: Wed Sep 18, 2019 12:15 am

### Re: ICE BOX

If x is less than 10-3, it can be considered negligible.

Nathan Rothschild_2D
Posts: 131
Joined: Fri Aug 02, 2019 12:15 am

### Re: ICE BOX

You also should check again at the end with the 5% dissociation rule. Divide your x by the initial and if it is greater than 5%, then you can't assume it's negligible.

Jacob Villar 2C
Posts: 105
Joined: Sat Aug 17, 2019 12:18 am

### Re: ICE BOX

When K is less than 10^-3, and you'll notice it is able to be approximated if x/initial concentration is less than 5%