A suspicious white powder was found in an abandoned backpack in the library. Ana

Question

A suspicious white powder was found in an abandoned backpack in the library. Analysis of the powder revealed that its composition is 49.48% carbon, 5.15% hydrogen, 28.87% nitrogen, and 16.49% oxygen by mass.

1. Determine the empirical formula of the compund. Show all steps and calculations.

2. Based on the molecular formulas listed below, what is the correct molecular formula and decide whether the DEA should be further investigating the owner of the backpack.

C8H9NO2 (Acetaminophen, Tylenol), C8H10N4O2(Caffeine), C17H21NO4 (Cocaine), C11H15NO2(Ecstasy), C10H15N (Methamphetamine), C17H19NO3 (morphine), C20H24N2O2(Quinine), C12H22O11*H2O (Lactose monohydrate, milk sugar).

Explanation / Answer

1). Assume 100 g of the compound is present. This changes the percents to grams:

Carbon ? 49.48 g

Hydrogen ? 5.15 g

Nitrogen ? 28.87 g

Oxygen ? 16.49 g

2) Convert the masses to moles:

C ? 49.48 g / 12 = 4.123

H ? 5.15 g / 1 = 5.15

N ? 28.87 / 14 =2.062
O ? 16.49 g / 16 = 1.03

3) Divide by the lowest, seeking the smallest whole-number ratio:

C ? 4.123 / 1.03 = 4.00

H?5.15 / 1.03 = 5

N ? 2.062 / 1.03 = 2

O? 1.03 / 1.03 = 1

4) Write the empirical formula:

C4H5N2O

2) From the above obtained emperical formula, correct molecular formula will be C8H10N4O2(Caffeine).

Thus, DEA should further investigate the owner of the backpack as caffeine is pyschoactive drug.

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