Question

what is the formula of acids

Answer 1

There is no particular general formula for Acids.

However, One similar finding in all acids is presence of H+ ions, Acids have a PH ranging from 0 to 6.

Some of the acids are HCl, HNO3, H2SO4.

If you are talking about carboxylic acid, Then they do share a common formula ;

The general formula of Carboxylic acid is $\sf \: C_{n} H_{2n+1}COOH$

They all have a same functional group - COOH.