The explosive known as RDX contains 16.22% carbon, 2.72% hydrogen, 37.84% nitrogen, and 43.22% oxygen by mass. Determine the empirical formula of the compound.

[C] : 16,22% (w/w)
[H] : 2,72% (w/w)
[N] : 37,84% (w/w)
[O] : 43,22% (w/w)
the emperical formula of the compound : .. ?

Answered

Step 1
Deterime mass of each elements in RDX

% (w/w) means X grams solute in 100 grams solvent.

[C] : 16,22% means 16,22 g of C in 100 g

[H] : 2,72% means 2,72 g of H in 100 g

[N] : 37,84% means 37,84 g of N in 100 g

[O] : 43,22% means 43,22 g of O in 100 g

Step 2
Determine moles of each elements

moles : mass / Ar

moles of C : 16,22 g / 12 g/moles
C : 1,352 moles

moles of H : 2,72 g / 1 g/moles
H : 2,72 moles

moles of N : 37,84 g / 14 g/moles
N : 2,703 moles

moles of O : 43,22 g / 16 g/moles
O : 2,701 moles

Step 3
Compare moles of each elements so we are going to find out the empirical formula of the compound.

m : moles

m. of C : m. of H : m. of N : m. O
1,352 : 2,720 : 2,703 : 2,701
——————————————— (1,352)
1 : 2,01 : 2,00 : 2,00
CH2N2O2
(CH2N2O2)n

So, the empirical formula of the compound is (CH2N2O2)n

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