Since I fell asleep in class, how do you find the molecular formula when the molecular mass is given?

find empirical formula first using percent composition data. once have empirical formula, divide formula weight of empirical formula molecular mass (60) see how many empirical formulas required produce molecular mass, multiply through multiplier. if assume have 100-g of starting material, percentages given convert grams.

c = 40-g x ( 1 mol c / 12.0-g c) = 3.33 mol c ----> 3.33 mol c / 3.33 mol = 1

h = 6.71-g x ( 1 mol h/ 1.01-g h) = 6.64 mol h ----> 6.64 mol h / 3.33 mol = 2


o = 53.29-g x 1mol o / 16-g o) = 3.33 mol o ----> 3.33 mol o / 3.33 mol = 1

(we had divide each of calculated moles smallest number of moles in order small whole whole numbers formula )

empirical formula = ch2o ---> formula mass = 12 + 2 + 16 = 30
molecular mass / empirical formula mass = 60/30 = 2 (this multiplier)

2 ch2o ---> c2h4o2 (molecular formula)

i'll share problem maybe guide me through problem way can solve other problems using one.

find molecular formula of 40.0% c, 6.71% h, 53.29% o
molecular mass = 60.

how solve this? in advance!

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