Percent Ionization

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Matt Sanruk 2H
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Percent Ionization

Postby Matt Sanruk 2H » Wed Jan 15, 2020 10:32 pm

So as long as the percent Ionization is less than 5%, we don't have to do the quadratic equation right?

claudia_1h
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Re: Percent Ionization

Postby claudia_1h » Wed Jan 15, 2020 10:34 pm

Yes, because the change to the initial concentration of the acid or base will be essentially zero. But usually the percent ionization doesn't come first, and is a step to confirm that approximating was okay (which you would do based on the value of K being <10^-3).

Katie Kyan 2K
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Re: Percent Ionization

Postby Katie Kyan 2K » Wed Jan 15, 2020 10:37 pm

Yes as long as the percent ionization is less than 5% of the initial concentration then the approximation is okay. If the equilibrium constant is less than 10^-3 then you do not have to use the quadratic equation and to check, you would calculate the percent ionization as confirmation.

Matt Sanruk 2H
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Re: Percent Ionization

Postby Matt Sanruk 2H » Wed Jan 15, 2020 10:52 pm

Oh ok this makes it a lot easier than the quadratic equation

Sanjana K - 2F
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Re: Percent Ionization

Postby Sanjana K - 2F » Thu Jan 16, 2020 9:38 am

If you don't use the quadratic equation, you still want to justify your reason for ignoring the "-x" terms in your equilibrium by saying that since x is less than 5% of the initial concentration, its change is negligible.

Jialun Chen 4F
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Re: Percent Ionization

Postby Jialun Chen 4F » Thu Jan 16, 2020 9:50 am

That is correct! And I believe that in homework problems the % ionization is under 5% excluding certain outliers.

EthanPham_1G
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Re: Percent Ionization

Postby EthanPham_1G » Sat Jan 18, 2020 4:29 pm

If the Ka or Kb is less than 10^-3 then you can approximate x and you don't have to use the quadratic equation.
If the percent ionization is less than 5% then your approximation is correct.

Bryan Chen 1H
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Re: Percent Ionization

Postby Bryan Chen 1H » Sat Jan 18, 2020 4:39 pm

yea, and then afterwards do the x value over initial concentration just to double check it is under 5%

Matt Sanruk 2H
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Re: Percent Ionization

Postby Matt Sanruk 2H » Mon Jan 20, 2020 8:01 pm

Cool, and even if the given concentration and ka/kb are both 10^-4 or lower it will still be the case right?

Juana Abana 1G
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Re: Percent Ionization

Postby Juana Abana 1G » Mon Jan 20, 2020 10:32 pm

Yes, as long as the percent Ionization is less than 5% we don't have to do the quadratic equation.

Bryan Chen 1H
Posts: 58
Joined: Mon Jun 17, 2019 7:24 am

Re: Percent Ionization

Postby Bryan Chen 1H » Fri Jan 24, 2020 6:22 am

Yea I always check to see if K is small but if its around like 10 to -3 or -4, you can do the approximation but make sure to check if x is less than 5% of the initial concentration

Matt Sanruk 2H
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Re: Percent Ionization

Postby Matt Sanruk 2H » Thu Jan 30, 2020 12:08 am

But there will always be a problem where the %ionization is not under 5 % of course...


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