1) Find mass and moles of carbon
n(C)=44.019.62×10−3=0.000219moles
m(C)=n×M=0.000219×12.01=0.00263g=2.63mg
2) Find mass and moles of hydrogen
n(H)=n(H2O)×2=18.023.94×10−3×2=0.000437moles
m(H)=n×M=0.000437×1=0.437mg
3) Find mass percent of chlorine in a sample
a) find mass of chlorine if silver nitrate:
n(AgCl)=Mm=143.3213.49×10−3=0.0000941mol
n(Cl)=n(AgCl)=0.0000941mol
m(Cl)=0.0000941×35.45=0.00334g=3.34mg
b) find mass percent of chlorine in silver nitrate
mass%(Cl)=5.323.34=0.627
4) Find mass and moles of chlorine in the first sample
m(Cl)=msample×mass%(Cl)=8.23×0.627=5.16mg
n(Cl)=Mm=35.455.16×10−3=0.000146mol
5) check up if there is an oxygen in a sample:
8.23=m(O)+m(C)+m(H)+m(Cl)
8.23=m(O)+2.63+0.437+5.16
m(O)=0.003mg (negligible)
6) find mole ratio
n(C):n(H):n(Cl)=0.000219:0.000438:0.000146=1.5:3:1=3:6:2
The formula is C3H6Cl2
7) Percent composition
mass percent %(c)=8.232.63×100%=32.0%
mass percent %(H)=8.230.437×100%=5.31%
mass percent %=8.235.16×100%=62.7%
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