Question

The Drug Enforcement Agency (DEA) confiscated substance during a drug raid. When the DEA chemists subjected the unknown substance to chemical analysis, they found that the substance had a molecular mass of 303 g/mole. Elemental analysis revealed the presence of carbon oxygen (21.12%), nitrogen (4.62%) the remaining elements of the substance was carbon and hydrogen. Determine a molecular formula and an index of hydrogen deficiency for this substance

Answer 1

Use the Rule of Thirteen to calculate the molecular formula for compound with known molecular mass.

Steps to be followed to calculate the molecular formula are as follows:

1. Find the base formula by dividing the molecular mass by 13 (sum of the masses of one carbon atom and one hydrogen atom).

Here, n is numerator and r is remainder.

Base formula is .

2. If the molecular formula contains other atoms along with carbon and hydrogen, then subtract the mass of a combination of carbons and hydrogen that equal to the mass of the other atoms.

C₂HO₄N₂