CHEM Assignment 18: %Composition
1. Penicillin, the first of a large number of antibiotics was discovered accidentally by Alexander Fleming in 1928, but he was never able to isolate it as a pure compound. Penicillin has the formula C14H20N2SO4. Calculate is molecular weight! Now compute the mass percent of H. %s are ("Part you're interested in / The total) x 100
Empirical and Molecular Formulas: see handout or text for help!
1. Analysis of nicotine gave 74.0% C, 8.7% H and 17.3 % N by mass and the MW of the compound was 162 g/mole. What is the molecular formula of nicotine?
2. An organic compound is 92.26% C and 7.74% H. Its molecular weight is around 80 g/mol. Determine the empirical and the molecular formulas.
3. Caffeine, a stimulant found in coffee, tea, and chocolate, contains 49.48% C, 5.15 % H, 28.87% N, and 16.49% O, by mass and has a MW of 194.2 g/mole. Determine the molecular formula of caffeine.
4. A sample of urea, the main ingredient in urine, contains 46.7% N, 6.71% H, 20.0% C, and 26.7% O. What is the empirical formula of urea? If the molecular weight is around 60 g/mol what is the molecular formula?
5. Analysis of an organic compound called ethylene glycol -properly known today as ethane diol (commonly known as "antifreeze") revealed that it contained 38.7% C, 9.7% H, and 51.6% O. The MW is around 65 g/mol. What are the empirical and molecular formulas?
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