Question

determine empirical and molecular formula of the compound containing 80/.c. 20/and whose molecular mass is 30​

Answer 1

Answer:

We have  

ethane

Explanation:

Explanation:

As with all these problems, it is usually assumed that we have a  

100

⋅

g

mass of unknown compound, and we work out the molar quantities:

And thus  

moles of carbon

=80/12.011=6.66 MOLES

moles of hydrogen

=20/1.008=19.8 mole

We divide the molar quantities thru by the SMALLER molar quantity:

C=6.66/6.66=1

H=19.8/6.66=2.97 (NEARLY 3)

And thus the  

empirical formula

 =CH3

And we know that the molecular formula is always a multiple of the empirical formula, and thus is terms of mass:

molecular formula=n ×empirical formula

But we have a molecular mass of  

30  amu

so,

30=n×(12.01+3*1.01)

clearly n=2

and the MOLECULAR FORMULA is  

C2H6

This is not a realistic problem, as few analysts would perform combustion on a liquid, and no analyst could perform combustion on a gas.

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