How do you recognize the formula for acids and bases?

Answer 1

It takes a little bit of practice before it becomes natural to you, but acids are usually (not always) proton/hydrogen donors and bases are usually (not always) proton/hydrogen acceptors.

I'm not sure how much you know about organic chemistry, but when a hydrogen is attached to a molecule that would be more stable without it (I'm using the words proton and hydrogen interchangeably), the hydrogen atom won't mind leaving the molecule - making it an acid. An example of this would be hydrochloric acid (HCl). When Cl- is alone, it is happy, because it has a full octet of electrons. It doesn't need the proton attached to it.

If a hydrogen is attached to a molecule that would probably like another hydrogen, such as sodium hydroxide (NaOH), this molecule would be called a proton acceptor - a base. When Na+ OH- gets its proton (H+), it becomes H2O and Na+, a much more stable conformation of elements.

There are a lot of factors that go into it though; there are no easy rules for telling the difference between acids and bases just by looking at their formula. Some other factors that go into it: hybridization, resonance stabilization, and electronegativity.

Answer 2

Acids typically start with "H" followed by a non-metal (e.g. HCl). Bases often contain a metal cation paired with a hydroxide ion (e.g. NaOH). Additionally, acids may have an "H" in their chemical formula, while bases often contain "OH".