The empirical formula is #C_5H_4# and its molar mass is 128.16 g/mol. What is the molecular formula?

1 Answer
anor277
Feb 14, 2016

The molecular formula is #C_10H_8#. How do we know?

Explanation:

The molecular formula is ALWAYS a mulitple of the empirical formula. Of course, the multiple might be #1#.

So #"MF" =(EF)_n# #=# #(5xx12.011*g*mol^-1+ 4xx1.00794*g*mol^-1)_n# #=# #(64.08)g*mol^-1xxn= 128.16*g*mol^-1.#

Clearly, #n=2#, and molecular formula #=# #C_10H_8#, probably napthalene.

Capisce?

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