# Chem question - dissociation constant **URL:** \ **Category:** Factual Questions\ **Created:** [March 22, 2007, 9:13pm UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080 "2007-03-22T21:13:58Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [March 22, 2007, 9:13pm UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080/1 "2007-03-22T21:13:58Z")
I am trying to find a pKb value for potassium carbonate, I have looked all over the “entar web”, and I cannot find a dissociation constant table of more than 15-30 entries. I must be **doing it all wrong** ™. Can someone point me to an online resource that will give me acid and base dissociation constants for, like, everything? TIA ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [March 23, 2007, 1:23am UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080/2 "2007-03-23T01:23:01Z")
bumpty bump ---
**Author:** ![Dr.Lao](https://avatars.discourse-cdn.com/v4/letter/d/2bfe46/32.png) [@Dr.Lao](https://boards.straightdope.com/u/Dr.Lao)\ **Post date:** [March 23, 2007, 12:44pm UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080/3 "2007-03-23T12:44:01Z")
Try looking up the pK[sub]a2[/sub] for carbonic acid. pK[sub]a[/sub] + pK[sub]b[/sub] = 14 ---
**Author:** ![HMS\_Irruncible](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hms_irruncible/32/7394_2.png) [@HMS\_Irruncible](https://boards.straightdope.com/u/HMS_Irruncible)\ **Post date:** [March 23, 2007, 1:13pm UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080/4 "2007-03-23T13:13:58Z")
[QUOTE=Dr. Lao] Try looking up the pK[sub]a2[/sub] for carbonic acid. pK[sub]a[/sub] + pK[sub]b[/sub] = 14 [/QUOTE] Thanks for the response, let me clarify and ask a question: 1. Mainly I was looking for a comprehensive database of dissociation constants, if anybody knows one. 2. Your answer suggests that knowing the pKa of carbonic acid is sufficient… does that imply that the basicity of potassium carbonate is the same as sodium carbonate is the same as calcium carbonate? ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [March 23, 2007, 6:20pm UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080/5 "2007-03-23T18:20:52Z")
pK[sub]a2[/sub] for carbonic acid is 10.33.(March’s Advanced Organic Chemistry is the best table I know of.) So pK[sub]b1[/sub] should be 3.67. I think it would be called pK[sub]b1[/sub] since it’s the first basicity, but I don’t know for sure. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [March 23, 2007, 6:21pm UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080/6 "2007-03-23T18:21:55Z")
> [@](#): > > does that imply that the basicity of potassium carbonate is the same as sodium carbonate is the same as calcium carbonate? Yes ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [March 23, 2007, 6:22pm UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080/7 "2007-03-23T18:22:26Z")
[QUOTE=Christopher] pK[sub]a2[/sub] for carbonic acid is 10.33.(March’s Advanced Organic Chemistry is the best table I know of.) So pK[sub]b1[/sub] should be 3.67. I think it would be called pK[sub]b1[/sub] since it’s the first basicity, but I don’t know for sure. [/QUOTE] That’s correct. ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [March 23, 2007, 6:32pm UTC](https://boards.straightdope.com/t/chem-question-dissociation-constant/397080/8 "2007-03-23T18:32:37Z")
> [@](#): > > 1. Mainly I was looking for a comprehensive database of dissociation constants, if anybody knows one. [Here is a pdf](http://daecr1.harvard.edu/pdf/evans_pKa_table.pdf)