The empirical formula for acetic acid is ##”CH”_2″O”##.

##”CH”_3″COOH”## can be written as ##”C”_2″H”_4″O”_2″##.

An empirical formula represents the lowest whole number ratio of in a compound.

The subscripts in the formula ##”C”_2″H”_4″O”_2″## can be reduced to the simplest whole number ratio by dividing the subscripts in the molecular formula by ##2##.

The empirical formula of acetic acid is ##”CH”_2″O”##.