I know the difference between a Strong Acid and a Strong Base. I understand that
ID: 504620 • Letter: I
Question
I know the difference between a Strong Acid and a Strong Base.
I understand that all the Strong Acids start with H and are 7 that you have to memorize.
I understand that all the Strong Bases are in the Group 1 and Group 2 of the periodic Table and you just add OH at the end...
My question is that I want to be able to differentiate a weak acid from a weak base. Not about strong acids and strong bases.
I have been making this question to my professor and he says that all the acids that are not in the list of the 7 strong acids are weak and all the bases that are not in the list of the strong bases are weak bases and I know that.
My question is that how can I differentiate a weak acid from a weak base.
This is not about Cojugate base of a weak acid or conjugate acid of a weak base
I want to know if there is a way to know for example if I just have "C5H5N" How can I know if this is a weak base or a weak acid?
Do all the weak bases have something in common that I can see and differentiate them from the weak acids? or do all the weak acids have something in common that I can see and differentiate them from a weak base?
Explanation / Answer
No you can not simply look at the formula and comment whether the given solution is weak or strong.
As you might be aware of the simple concept that says, if a molecule is able to donate a proton it is acid and if it accepts the proton it is base.
So basically the whole things depends on this concept. How readily a molecule can accept or donate a proton makes it strong or weak.
Strong acids will readily loose their proton whereas the weak acids will not dissociate completely. Same is the case with bases.
Now when you look for the ionisation of acid or bases, you look for their ionisation constants or how much amount of them are being dissociated. This is given by Ka and kb. Pka and pKb are negative logarithms of them respectively.
So you need to calculate pka and pkb now. More the pka of solution, lesser will be its acidic strength . For weak acids the range is 2 to 14
Likewise for bases, smaller the value of pkb stronger will be it's basic strength. Again for weak bases, the value ranges from 2 to 13.