Question

An unknown compound is discovered in a raid on a terrorist organization; it is believed that the compound is Sarin. When a 10.0-gram sample of this compoun is completely combusted, 15.6 g CO2 and 6.4 g H20 are produced, along with other combustion products. Using numerical calculations, prove that this unknown compound can not be Sarin.

Answer 1

Given:

Mass of the unknown compound (believed to be Sarin) = 10.0 g

Mass of CO2 produced = 15.6 g

Mass of H2O produced = 6.4 g

To determine:

If the unknown compound is Sarin

Explanation:

The molecular formula for Sarin is: C₄H₁₀FO₂P

Based on stoichiometry the C:H ratio = 4:10 i.e 2:5

Now, from the combustion data:

# moles of CO2 produced = # moles of C present in the unknown sample

Similarly, (# moles of H2O produced)*2 = # moles of H present in the unknown sample

# moles of CO2 = 15.6 g/44 g.mol-1 = 0.354 moles

# moles of H2O = (6.4 g/ 18 g.mol-1 )* 2 = 0.711 moles

The C:H ratio = 0.354 : 0.711 = 1:2

Ans: Since the C:H ratio does not match the actual stoichiometry based on the molecular formula, the unknown compound is not Sarin.