How do you calculate the molecular formula of a compound with the empirical formula #C_n H_(2n) O# and a molar mass of 150 g/mol?

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Answer 1 · 2017-04-10T13:56:05

Divide the empirical formula into the the molecular mass to find the number n and then put n into the chemical formula

It would help if there was an n under the O but assume the formula has an n under the O the empirical formula has the ratio of

1 #C# : 2 #H# : 1 #O#
We now define the mass if n=1

1x #C# = 1 x12u = 12u (=12 gram/mol)

2x #H# = 2 x 1u = 2u

1 x #O# = 1 x 16u = 16u
Adding them all together gives the mass per n=1

12 + 2 + 16 = 30 g/mol

Divide 150 g/mol by 30 g/mol to find the number of empirical units (which is n).

# 150/30 = 5#

So we get n = 5, putting this back into the formula gives the solution

# C_5H_10O_5#