ICE BOX

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

ICE BOX

Postby 205150314 » Sun Jan 26, 2020 9:54 pm

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

Postby Hannah Pham » Sun Jan 26, 2020 9:55 pm

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

Charysa Santos 4G
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Re: ICE BOX

Postby Charysa Santos 4G » Sun Jan 26, 2020 10:01 pm

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

Anna Heckler 2C
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Re: ICE BOX

Postby Anna Heckler 2C » Sun Jan 26, 2020 10:02 pm

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

Postby 105311039 » Sun Jan 26, 2020 10:03 pm

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

Gabriel Ordonez 2K
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Re: ICE BOX

Postby Gabriel Ordonez 2K » Sun Jan 26, 2020 11:24 pm

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
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Re: ICE BOX

Postby Jesse Anderson-Ramirez 3I » Sun Jan 26, 2020 11:26 pm

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

Ashley Nguyen 2L
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Re: ICE BOX

Postby Ashley Nguyen 2L » Sun Jan 26, 2020 11:33 pm

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

Angus Wu_4G
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Re: ICE BOX

Postby Angus Wu_4G » Sun Jan 26, 2020 11:35 pm

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
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Joined: Wed Sep 11, 2019 12:17 am

Re: ICE BOX

Postby vanessas0123 » Tue Jan 28, 2020 10:15 am

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

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

Re: ICE BOX

Postby Kishan Shah 2G » Tue Jan 28, 2020 12:45 pm

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
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Joined: Sat Aug 24, 2019 12:16 am

Re: ICE BOX

Postby 005384106 » Tue Jan 28, 2020 12:58 pm

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

Jialun Chen 4F
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Re: ICE BOX

Postby Jialun Chen 4F » Tue Jan 28, 2020 1:09 pm

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
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Joined: Wed Sep 18, 2019 12:15 am

Re: ICE BOX

Postby Juana Abana 1G » Sun Feb 02, 2020 11:40 pm

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
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Joined: Wed Nov 14, 2018 12:19 am

Re: ICE BOX

Postby Areli C 1L » Sun Feb 09, 2020 8:24 pm

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
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Re: ICE BOX

Postby Matthew ILG 1L » Sun Feb 09, 2020 8:27 pm

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

zfinn
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Re: ICE BOX

Postby zfinn » Sun Feb 09, 2020 8:34 pm

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

Eesha Chattopadhyay 2K
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Re: ICE BOX

Postby Eesha Chattopadhyay 2K » Sun Feb 09, 2020 8:36 pm

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

Postby J Medina 2I » Sun Feb 09, 2020 8:39 pm

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
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Joined: Fri Sep 28, 2018 12:16 am

Re: ICE BOX

Postby Owen-Koetters-4I » Sun Feb 09, 2020 9:14 pm

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

KHowe_1D
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Re: ICE BOX

Postby KHowe_1D » Sun Feb 09, 2020 9:52 pm

X is too small when K<10^-3

AronCainBayot2K
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Re: ICE BOX

Postby AronCainBayot2K » Sun Feb 09, 2020 9:54 pm

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

Catherine Daye 1L
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Re: ICE BOX

Postby Catherine Daye 1L » Sun Feb 09, 2020 10:21 pm

When it’s smaller than 10^-3

Sean Tran 2K
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Re: ICE BOX

Postby Sean Tran 2K » Sun Feb 09, 2020 11:30 pm

If X is less than 10^-3

Maria Poblete 2C
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Re: ICE BOX

Postby Maria Poblete 2C » Sun Feb 09, 2020 11:32 pm

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

Postby Nathan Rothschild_2D » Sun Feb 09, 2020 11:37 pm

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
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Joined: Sat Aug 17, 2019 12:18 am

Re: ICE BOX

Postby Jacob Villar 2C » Sun Feb 09, 2020 11:43 pm

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%

Ashley Alvarado 2C
Posts: 45
Joined: Sat Aug 17, 2019 12:16 am

Re: ICE BOX

Postby Ashley Alvarado 2C » Mon Feb 10, 2020 9:56 pm

X will be too small if it is less than 5% of the initial and if K<10^-3.


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