Percent Ionization
Moderators: Chem_Mod, Chem_Admin
-
- Posts: 131
- Joined: Wed Sep 18, 2019 12:21 am
Percent Ionization
So as long as the percent Ionization is less than 5%, we don't have to do the quadratic equation right?
-
- Posts: 111
- Joined: Fri Aug 09, 2019 12:16 am
Re: Percent Ionization
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).
-
- Posts: 106
- Joined: Fri Aug 09, 2019 12:16 am
- Been upvoted: 1 time
Re: Percent Ionization
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.
-
- Posts: 131
- Joined: Wed Sep 18, 2019 12:21 am
-
- Posts: 102
- Joined: Sat Sep 07, 2019 12:17 am
- Been upvoted: 1 time
Re: Percent Ionization
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.
-
- Posts: 108
- Joined: Sat Sep 07, 2019 12:16 am
Re: Percent Ionization
That is correct! And I believe that in homework problems the % ionization is under 5% excluding certain outliers.
-
- Posts: 104
- Joined: Sat Jul 20, 2019 12:17 am
Re: Percent Ionization
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.
If the percent ionization is less than 5% then your approximation is correct.
-
- Posts: 58
- Joined: Mon Jun 17, 2019 7:24 am
Re: Percent Ionization
yea, and then afterwards do the x value over initial concentration just to double check it is under 5%
-
- Posts: 131
- Joined: Wed Sep 18, 2019 12:21 am
Re: Percent Ionization
Cool, and even if the given concentration and ka/kb are both 10^-4 or lower it will still be the case right?
-
- Posts: 100
- Joined: Wed Sep 18, 2019 12:15 am
Re: Percent Ionization
Yes, as long as the percent Ionization is less than 5% we don't have to do the quadratic equation.
-
- Posts: 58
- Joined: Mon Jun 17, 2019 7:24 am
Re: Percent Ionization
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
-
- Posts: 131
- Joined: Wed Sep 18, 2019 12:21 am
Re: Percent Ionization
But there will always be a problem where the %ionization is not under 5 % of course...
Return to “Equilibrium Constants & Calculating Concentrations”
Who is online
Users browsing this forum: No registered users and 7 guests