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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: sarah9625 on October 19, 2007, 09:20:55 PM

Title: Weak bases
Post by: sarah9625 on October 19, 2007, 09:20:55 PM
What are some examples of weak bases?
 I have google this question and found only one, NH3, there has to be more than that. Do you know of any others?
Title: Re: Weak bases
Post by: is3zzz on October 19, 2007, 09:34:19 PM
Methylamine is another one i can think of....
Title: Re: Weak bases
Post by: Padfoot on October 19, 2007, 09:56:56 PM
The conjugates of common strong bases, another common one I know is alanine.
Title: Re: Weak bases
Post by: sarah9625 on October 19, 2007, 10:02:08 PM
I am guessing that there is way more strong bases than weak ones, right?
Title: Re: Weak bases
Post by: Padfoot on October 19, 2007, 10:12:46 PM
I meant conjugates of common strong ACIDS by the way.

As for:
Quote from: sarah9625 on October 19, 2007, 10:02:08 PM
I am guessing that there is way more strong bases than weak ones, right?
??? I can think of more strong bases than I can weak but this is probably just because I've used strong bases more  :-\
Title: Re: Weak bases
Post by: LQ43 on October 19, 2007, 11:26:12 PM
methylamine is a good start but if you look at the general formula RCH2N, then you can get a ton of weak bases by substituting alkyl groups for R,


there are actually many more weak acids and bases than strong ones. does your textbook not give a list of strong acids, there aren't that many

I'm surprised you can only get NH3 from googling "weak bases"
"http://www.science.uwaterloo.ca/~cchieh/cact/c123/wkacids.html
Title: Re: Weak bases
Post by: ashrafabdeljaber on October 19, 2007, 11:30:08 PM
Magnesium hydroxide Mg(OH)2 is a weak base
Title: Re: Weak bases
Post by: sarah9625 on October 20, 2007, 12:33:51 AM
Thanks, LQ43 thats exactly what I was trying to find. Here's a snack:)
Title: Re: Weak bases
Post by: LQ43 on October 20, 2007, 10:57:28 AM
Quote from: ashrafabdeljaber on October 19, 2007, 11:30:08 PM
Magnesium hydroxide Mg(OH)2 is a weak base

well, strictly speaking, Mg(OH)2 is a slightly soluble ionic compound that also happens to be a base. Whatever amount that is soluble does dissociate 100% so it is in fact a strong base.

Quote from: sarah9625 on October 20, 2007, 12:33:51 AM
Thanks, LQ43 thats exactly what I was trying to find. Here's a snack:)

well, thanks but I should really have prompted you to look again,  ;)
Title: Re: Weak bases
Post by: Borek on October 20, 2007, 11:32:10 AM
Quote from: LQ43 on October 20, 2007, 10:57:28 AM
Quote from: ashrafabdeljaber on October 19, 2007, 11:30:08 PM
Magnesium hydroxide Mg(OH)2 is a weak base

well, strictly speaking, Mg(OH)2 is a slightly soluble ionic compound that also happens to be a base. Whatever amount that is soluble does dissociate 100% so it is in fact a strong base.

That's not quite true. pK for

Mg2+ + OH- = MgOH+

is somewhere between 2 and 3. That makes Mg(OH)2 in a way comparable with sulphuric acid - strong for the first dissociation step, realitively weak for the second.
Title: Re: Weak bases
Post by: LQ43 on October 20, 2007, 11:35:08 AM
thanks Borek, that went deeper then I was thinking....