The empirical formula of a compound is CH. The experimental molar mass is 78.12 g/mol. How do you determine the molecular formula of the compound?

1 Answer
anor277
Jan 19, 2017

The #"molecular formula"# is always a whole number multiple of the #"empirical formula"#.

Explanation:

And thus: #"molecular formula"=nxx"(empirical formula)"#.

We take the given empirical formula, work out its mass, and then solve for #n#.

So #78.23*g*mol^-1=nxx(12.011+1.00794)*g*mol^-1#

Where of course, #12.011# and #1.00794# are the atomic masses of carbon and hydrogen in #g*mol^-1#,

#n=(78.23*g*mol^-1)/((12.011+1.00794)*g*mol^-1)=6#

And thus the molecular formula #-=# #(CH)_6# or #C_6H_6#. What is the likely name of this molecule?

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