Acid or base: is there a way to tell from the molecular formula?

[growingpains]

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For example, how do you know that Ca(OH)2 is a base?

 

[folktale]

On that case, think Arrhenius. It has an OH, therefore, it's a base. But let's say it's a carboxylic acid H3CCO2H, then it has the H that can dissociate instead of an OH. It's just a matter of seeing the molecule from the formula.

 

[MedPR]

On that case, think Arrhenius. It has an OH, therefore, it's a base. But let's say it's a carboxylic acid H3CCO2H, then it has the H that can dissociate instead of an OH. It's just a matter of seeing the molecule from the formula.

This isn't really a good rule to follow. COOH have OH groups, so does water, yet both can act as acids.

If something is going to form OH- in aqueous solution, donate an electron pair, or accept a proton, it is a base.

 

[Temperature101]

For example, how do you know that Ca(OH)2 is a base?

The best way to identify acids and bases is to know the definition of Bronsted/ Lowry, Arrhenius and Lewis. The one you gave is an easy one to identify, but there some melecules that you have to know and understand these definitions in order to know if they are acid or not.

 

[growingpains]

Ah, I do understand the definitions. So it seems like it's a matter of drawing out the structures (including resonance).