What is the Empirical and Molecular Formula of Caffeine?

[haengbon]

Homework Statement

What is the Empirical and Molecular Formula of caffeine, given these information:

0.376g caffeine would yield to 0.682 CO₂ , 0.174g H₂O and 0.110g N. The molecular weight if caffeine is 194 g/mole.

Homework Equations

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The Attempt at a Solution

0.682 CO₂ \rightarrow gC = 0.186 gC
0.174g H₂O\rightarrow gH = 9.735 x 10^-03 gH
0.110gN \rightarrow0.110 gN

0.376g sample = gC + gH + gN + gO
0.376g sample - 0.186 gC - 9.735 x 10^-03 gH - 0.110gN = gO
gO = 0.070


C= 0.186/12.01 = 0.15/.004375 = 3.42 \approx 3

H= .009735/1.008 = .009735/.004375 = 2

N= 0.110/14.01 = .00785/.004375 = 1.7 \approx 2

O= 0.070/16.00 = .004375/.004375 = 1

EF: C₃H₂N₂O

n= \frac{MW}{EFW}

n= \frac{194}{82.066}

n=2

MF= n(EF)
MF= 2(C₃H₂N₂O)

MF= C₆H₄N₄O₂

Is this correct? :/ I think It's not but I hope it is! :)

 

[Greg Bernhardt]

The molecular formula for caffeine is C8H10N4O2.