Question

1.A compound consists of 65.45% C, 5.492% H, and 29.06% O on a mass basis and has a molecular mass of 110 g/mol. Determine the molecular formula of the compound.

2. What is the formula weight of iron (II) sulfate? Answer in units of g/mol.

3. What is the % nitrogen by weight in 2.368 mol of ammonium sulfide? Answer in units of %.

Answer 1

Take a 100 g sample. This gives you
65.45 g C
5.49 g H
29.06 g O

Convert to mols.
65.45/12 = ?
5.49/1 = ?
29.06/16 = ?

Now find the ratio of those elements to each other. The easy way to do that is to divide the smallest number by itself; then divide the other two numbers by the same small number.

2. FeSO4. All you need to do is to add atomic mass Fe to atomic mass of S to atomic mass of 4*oxygen.

3. Ammonium sulfide is (NH4)2S.
%N is same in the compound no matter how many moles you have.
%N = (2*atomic mass N/molar mass (NH4)2SO4)*100 = ?