## ignoring x

marcus lin 1E
Posts: 54
Joined: Fri Sep 28, 2018 12:28 am

### ignoring x

so for some of the ICE table calculations we ignore x and just pretend it's 0, when do we do that?

BenJohnson1H
Posts: 68
Joined: Fri Sep 28, 2018 12:17 am

### Re: ignoring x

When k is equal to or less than 10^3 you can omit any X that is being added or subtracted. To check, see if the dissociation of the acid/base is equal to or lower than 5%.

Miriam Sheetz 2B
Posts: 64
Joined: Fri Sep 28, 2018 12:25 am

### Re: ignoring x

You can ignore x in the ice table when the K value is less than 10^-3 because it the percent ionization will be less than 5%.

Erin Kim 2G
Posts: 75
Joined: Fri Sep 28, 2018 12:26 am

### Re: ignoring x

You can ignore x in some instances because the amount that dissociates will be so little that it is insignificant to the overall decrease in the molarity. If the K value is extremely small, namely less than 10^-3, it means that reactants are favored in the reaction and so little of the reactants will be converted into products and therefore, the x value is so little and its subtraction is negligent.

Ian Marquez 2K
Posts: 66
Joined: Fri Sep 28, 2018 12:16 am
Been upvoted: 2 times

### Re: ignoring x

Also, it is important to keep in mind that x is not actually 0 because if you plug in 0 for all x's it will be impossible to solve for x. However, it is useful in approximations to make the calculations more simple as the other replies have stated.

sonalivij
Posts: 70
Joined: Fri Sep 28, 2018 12:27 am

### Re: ignoring x

Keep in mind that x is only considered to be 0 when it is being added or subtracted to a number, not when it is alone and being multiplied

Kevin Tang 4L
Posts: 83
Joined: Fri Sep 28, 2018 12:28 am

### Re: ignoring x

You can ignore x in an equilibrium equation when the percent deprotonation or protonation is less than 5%. This is because x will be negligible in the denominator related to the other initial value.

Hope this helps correct me if i'm wrong.

Sapna Ramappa 1J
Posts: 63
Joined: Fri Sep 28, 2018 12:24 am

### Re: ignoring x

If the K value is less than 10^-3, you can ignore the x in the denominator if it is being added or subtracted to the initial concentration. This is because it'll make such a minute difference in the equilibrium concentration as a whole. Be careful that you don't just substitute all the x values with 0!

Diana Sandoval 1K
Posts: 61
Joined: Fri Sep 28, 2018 12:25 am
Been upvoted: 1 time

### Re: ignoring x

When k is equal to or less than 10^3.

Tony Chung 2I
Posts: 60
Joined: Fri Sep 28, 2018 12:19 am

### Re: ignoring x

you can ignore x when youre approximating. this is when your k value is less than or equal to 10^-3

Luis_Yepez_1F
Posts: 50
Joined: Fri Sep 28, 2018 12:18 am

### Re: ignoring x

You can ignore x when k is less than 1x10^-3

Mark 1D
Posts: 63
Joined: Fri Sep 28, 2018 12:18 am

### Re: ignoring x

X is zero if follows 5% rule or if K is less than 10^-3. Therefore no need to use quadratic equation

jlinwashington1B
Posts: 65
Joined: Fri Sep 28, 2018 12:22 am

### Re: ignoring x

X can be ignored when k is less than 1x10^-3

Sarah_Kang_2K
Posts: 72
Joined: Fri Sep 28, 2018 12:23 am

### Re: ignoring x

You can ignore x when approximating (when K<10^-3), but make sure to check your work after to make sure x is indeed less than or equal to 5% deprotonation!

sonalivij
Posts: 70
Joined: Fri Sep 28, 2018 12:27 am

### Re: ignoring x

A good way to check if your approximation was valid is to see if x is less than 5% of the initial concentrations

Nghi Nguyen 2L
Posts: 61
Joined: Fri Sep 28, 2018 12:18 am

### Re: ignoring x

when K is less than 1*10^-3 but I think Dr. Lavelle said on the midterm that he wants use to always use the quadratic formula so I can only assume that applies to the final as well

Jacqueline Duong 1H
Posts: 61
Joined: Fri Sep 28, 2018 12:28 am

### Re: ignoring x

We can ignore x when the 5% rule applies to it, which is when x is less than 5% of the initial concentration.