posted by Jake .
Carminic acid,a naturally occuring red pigment extracted from the cochineal insect, contains only C,H,and O. It was commonly used as a dye in the first half of the nineteenth century. It is 53.66% C and 4.09% H by mass. A titration of the 0.3602 g sample pf the carminic acid requires 18.02 Ml of 0.0406 M NaOH to neutralize. Assuming there is only 1 acidic hydrogen per molecule, what is the molecular formula of carminic acid?
I know that carminic acid is a monoprotic acid and that I have to find the empirical formula fist then the gram molar weight, but how do I set this problem up in order to solve it? Do I add up the given percentages and then subtract them from 100% to find the percent of O?