The empirical formula of a compound is #CH#. If the molar mass of this compound is about 78 g, what is its molecular formula?

1 Answer
anor277
Apr 10, 2016

#C_6H_6#

Explanation:

The #"empirical formula"# is the simplest whole number ration that defines constituent atoms in a species. The #"molecular formula"# is always a multiple of the #"empirical formula"#.

Given the above: #"molecular formula" =nxx("empirical formula")#

Thus #"molecular formula" = 78.0*g*mol^-1 = n(12.011+1.00794)*g*mol^-1#

#n=78/(12.011+1.00794)# #=# #6#.

And #"molecular formula"= C_6H_6#

Sometimes (but not here!) #"molecular formula"# #-=# #"empirical formula"#, i.e. the mulitple #n# #=# #1#.

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