## Approximating X

JohnWalkiewicz2J
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### Approximating X

When solving ICE tables or a equilibrium concentration for a R/P, for what value of Q/K do you approximate x, so you don't have to use the quadratic formula. Thnx in advance!

EthanPham_1G
Posts: 104
Joined: Sat Jul 20, 2019 12:17 am

### Re: Approximating X

If the K value is smaller than 10^-4 then you can approximate the x value. You can double check this by using the 5% rule. If the percent ionization is 5% or less then it is ok to approximate the x value.

Sartaj Bal 1J
Posts: 101
Joined: Thu Jul 25, 2019 12:17 am

### Re: Approximating X

Minor detail, but in response to the above, I believe it's okay to approximate if the K value is 10^-4 or smaller.

Izzie Capra 2E
Posts: 103
Joined: Sat Sep 07, 2019 12:19 am

### Re: Approximating X

Make sure you always check using the 5% ionization rule when approximating, there are some odd cases where the K value is incredibly small but there can be a discrepancy of greater than 5%. In this case, you would have to use the quadratic formula.

William Chan 1D
Posts: 102
Joined: Sat Sep 14, 2019 12:15 am

### Re: Approximating X

The general rule is that, if k is smaller than 10^-4, then it should be safe to assume that the change in concentration is negligible and that x can be ignored. Of course, you can always check that the difference is less than 5% to make sure.

Manav Govil 1B
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Joined: Sat Sep 07, 2019 12:19 am

### Re: Approximating X

This is a helpful link if you're confused!

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

### Re: Approximating X

If the k value is very small (i.e. less than 10^-4) then you can approximate.

Tanmay Singhal 1H
Posts: 143
Joined: Sat Jul 20, 2019 12:16 am

### Re: Approximating X

if x is very small. i believe less than 5%

ramiro_romero
Posts: 90
Joined: Sat Sep 07, 2019 12:16 am

### Re: Approximating X

I specifically remember Lavelle mentioning in one of his lectures that if the value for K is less than (10^-3), then it is okay to approximate for x. Usually, just consider your initial moles of reactant and that the x value should leave no significant difference after subtracted from the moles of reactant (When approximated).

Jessa Maheras 4F
Posts: 121
Joined: Fri Aug 02, 2019 12:16 am

### Re: Approximating X

Manav Govil 1B wrote:This is a helpful link if you're confused!

Thank you this link is very helpful!

Emily Lo 1J
Posts: 50
Joined: Thu Sep 19, 2019 12:16 am

### Re: Approximating X

If your K value is less than 1.0*10^-3, then you can assume that the x value will not greatly effect the values in your equation. So if the K value is that small, you can assume that the x value in the denominator is 0.

Jarrett Peyrefitte 2K
Posts: 102
Joined: Sat Aug 24, 2019 12:16 am

### Re: Approximating X

ff the K value is smaller than 5% aka 10^-4, then x can be approximated

Ayushi2011
Posts: 101
Joined: Wed Feb 27, 2019 12:17 am

### Re: Approximating X

Use the 5% rule, if X is less than that then we can approximate.

Gurmukhi Bevli 4G
Posts: 49
Joined: Wed Nov 14, 2018 12:20 am

### Re: Approximating X

You can approximate the x value provided K<10^-4 (or smaller), and as already stated, you can cross check using the 5% ionization rule.

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