Vitamin C (ascorbic acid) contains 40.92 % C, 4.58% H, 54.50 % O, by mass. The experimentally determined molecular mass is 176 amu. What are the empirical and chemical formulas for the ascorbic acid?​

Answer 1

Hello, Leslie,

Set up a table with the elements and enter the data, as below. The column "AMU TTL" is calculated by taking the molar mass of 176 amu and multiplying it times each of the Mass % figures. Make a column labelled ATOMS, and divide the AMU TTL by the AMU for each element. This will provide a very close estimate of how many atoms of each are in the ascorbic acid molecule.

Now all we need to do is round to the nearest whole number of atoms, and check to see if the resulting empirical formula does amount to a molar mass of 176.

C₆H₈O₆ This is a formula that adds to a molecular weight of 176.1, within a tolerable 0.1 amu of the experimental result.

Bob