Carminic acid, a naturally occurring red pigment extracted from the cochineal insect, contains only carbon, hy?

Question

Carminic acid, a naturally occurring red pigment extracted from the cochineal insect, contains only carbon, hydrogen, and oxygen. 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 required 18.02 mL of 0.0406 M NaOH to neutralize 0.3602 g carminic acid. Assuming that there is only one acidic hydrogen per molecule, what is the molecular formula of carminic acid?

Johathan Wehner · Accepted Answer

Use the titration to determine the MM of Carminic Acid.(0.01802L)(0.0406M/L) = 0.0007316 moles NaOH Assuming 1 acidic H per molecule, 0.3602g represents 0.0007316 moles of Carminic Acid.Your MM of Carminic Acid is: 0.3602g/0.0007316moles = 492.337The percentage of O must be 100.00 – (53.66 + 4.09) = 42.25Change these to weight fractions by dividing each by 100.C = 0.5366w/f H = 0.0409w/f O = 0.4225w/f Multiply the MM of Carminic Acid by the w/f of each element then divide that by the MM of that same element.For C: (492.337)(0.5366)/12.01115 = 21.995 round to 22For H: (492.337)(0.0409)/1.00797 = 19.977 round to 20For O: (492.337)(0.4225)/ 15.9994 = 13.001 round to 13Your EMPIRICAL FORMULA is C22H20O13Ideed, that is the correct formula for Carminic Acid.

Haylie Ernser DVM

Carminic acid, a naturally occurring red pigment extracted from the cochineal insect, contains only carbon, hy?

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