x is small approximation

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Jessica Chen 2C
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x is small approximation

Postby Jessica Chen 2C » Sun Jan 12, 2020 2:46 pm

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

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Re: x is small approximation

Postby JohannaPerezH2F » Sun Jan 12, 2020 2:48 pm

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

Areena H 2K
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Re: x is small approximation

Postby Areena H 2K » Sun Jan 12, 2020 4:40 pm

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.

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Re: x is small approximation

Postby faithkim1L » Wed Jan 15, 2020 1:56 pm

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.

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Re: x is small approximation

Postby ThomasNguyen_Dis1H » Wed Jan 15, 2020 2:09 pm

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

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Re: x is small approximation

Postby Veronica_Lubera_2A » Wed Jan 15, 2020 3:21 pm

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
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Re: x is small approximation

Postby Astrid Lunde 1I » Wed Jan 15, 2020 3:27 pm

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

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