Some Basic Concepts Of Chemistry Question 147
Question: A gaseous compound is composed of 85.7% by mass of carbon and 14.3% by mass of hydrogen. Its density is 22.8 g/L at 350 K and 1.0 atm pressure. Calculate the molecular formula of compound.
Options:
A) $ C _5H _{10} $
B) $ C _6H _{12} $
C) $ C _4H _8 $
D) $ C _8H _{18} $
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Answer:
Correct Answer: C
Solution:
[c] $ d=\frac{pM}{RT} $
$ M=\frac{dRT}{pM}=\frac{2.28\times 0.081\times 300}{1}=56.20,\text{g/mol} $
Ratio
$ \Rightarrow $ $ \frac{85.7}{12}:\frac{14.3}{1}=1:2 $
Empirical formula of compound $ ={{(CH _2)} _{n}} $
$ n=\frac{56.20}{12+2}=4 $ Molecular formula $ =[CH _2]\times 4=C _4H _8 $
