## x is small approximation

Jessica Chen 2C
Posts: 103
Joined: Thu Jul 11, 2019 12:17 am

### x is small approximation

How do we determine when we can use the "x is small" approximation? Do we look at the value of K for this?

JohannaPerezH2F
Posts: 94
Joined: Wed Sep 18, 2019 12:18 am

### Re: x is small approximation

according to the video module, we can assume K is small when it is approximate 10^-4 or smaller

Areena H 2K
Posts: 81
Joined: Wed Dec 05, 2018 12:18 am

### Re: x is small approximation

When K is really small we can say that the difference would be negligible or very small so we can use that to exclude X.

faithkim1L
Posts: 105
Joined: Fri Aug 09, 2019 12:17 am

### Re: x is small approximation

When Kc is a very small number, we know that there will be a large amount of reactant and a small amount of product (Kc is products over reactant, so the larger the denominator the smaller Kc). When Kc is 10^-3 or smaller, we can assume that the change (x) is so small that is makes a negligible effect on the initial molarities of the reactants. This is when we can "ignore" x in an equilibrium calculation.

ThomasNguyen_Dis1H
Posts: 102
Joined: Fri Aug 30, 2019 12:17 am

### Re: x is small approximation

When K is smaller than 10^-3 you can approximate x

Veronica_Lubera_2A
Posts: 106
Joined: Sat Sep 14, 2019 12:16 am
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### Re: x is small approximation

Today in lecture he mentioned that 10^-4 is the boundary, so anything 10^-4 and smaller can be approximated. However, he said that if K does equal 10^-4, you should double check your answer at the end (by plugging it back in) to see if there is a difference between your answer and the given because in some rare situations it could change the answer.

Astrid Lunde 1I
Posts: 103
Joined: Sat Sep 07, 2019 12:16 am

### Re: x is small approximation

We can approximate if x is less then 1.0 x 10^-4.