Convert CO2 to C, H2O to H.
46.18 mg x (atomic mass C/molar mass CO2) = 46.18 x 12/44 = approx 13
7.10 x (2*atomic mass H/molar mass H2O) = 7.10 x 2/18 = about 0.8
mg O = 46.18-13 - 0.8 = about 8.
Convert to mols.
C = 13/12 = about 1
H = 0.8/1 = 0.8
O = 8/16 = 0.5
Find the ratio of C to H to O which will be about 2 C to 1.5 H to 0.5 O or approx C4H3O2 for the empirical formula. You should check ALL of the calculations above.
Since 1/4 mol has a mass of 41.5 then a mol is 41.6*4 = 166.
empirical mass x whole number = 166 or
83 x whole number = 166 or whole number = 2 so molecular formula is (C4H3O2)2 = C8H6O4
Remember to check all of those numbers above and use more accurate numbers.
Terephthalic acid is an important chemical used in the manufacture of polyesters and plasticizers. It contains only C, H, and O. Combustion of 21.79 mg terephthalic acid produces 46.18 mg CO2 and 7.10 mg H2O. If 0.250 mol of terephthalic acid has a mass of 41.5 g, determine the molecular formula of terephthalic acid. (Type your answer using the format CO2 for CO2.)
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