chemistry empirical formulas
posted by princess on .
Calculate the empirical formula of a molecule with the following percent compositions: 55.0% gallium (Ga) and 45.0% fluorine (F).
mass of 100g #of Moles in 100g
of the compound
Ga55.0% _____ ______
F45.0% ______ _______
c. Determine the molecular formula of a molecule having an empirical formula of NH2 and a molar mass of 32 g/mol.

Take a 100 g sample which will give you
55.0 g Ga and
45.0 g F
Convert to mols.
55.0/atomic mass Ga = ?
45.0/atomic mass F = ?
Now find the ratio of the elements to each other with the smallest being 1.00. The easy way to do this is to divide the smaller number by itself(which gives 1.00), then divide the other number by the same small number. Round to whole numbers. Post your work if you get stuck.
c.
empirical formula = NH2. empirical formula mass = 14 + 2(1.00) = 16
molar mass = 32
16*n = 32
n = 2; therefore, the molecule consists of two units of NH2.
(NH2)2 or N2H4.
Check. 2N + 4H = 2(14) + 4(1) = 28 + 4 = 32. must be right. 
since i don't have a teacher. I tried and this is what i came up with.
55.0/atomic massGa
55.0/69.723= 1.27 (rounded)
45.0/atomic massF
45.0/18.998404= 2.37 (rounded)
If this is corect what do I do after this. If not can you help me with an headstart please.?