help with my chemistry homework on empirical/molecular formula?

Question

1. The formula of a complex salt A is [Cu(Nh3)x(H2O)y]SO4 and analysis produced the following composition by mass : Cu - 24.1% , H-6.1% , O-36.4%. Calculate the values of x and y and hence determine the percentage by mass of sulphur in A

2. When 585 mg of the salt UO(C2O4).6H2O was left in a vacuum desiccator for two hours , the mass was reduced to 535 mg. Predict the formula for the resulting substance.

Answer 1

i will search the molecular mass of the product
1) Cu mass 63.5 =24.1% =05.241M
so M = 63.5/0.241= 263.7
O = 0.364*263.7=96 so 6O , you have 4oxygen for SO4 so , you have 2 for 2 molecules of H2O y=2
H = 0.061*263.7= 16 so H16, 4 for 2 molecules of H20 , 16-4 =12 so x=4
Formula [Cu(NH3)4,(H2O)2]SO4
% mass of sulfur 32/263.7 =0.121= 12.1%

2)mass of your product 238+12*2+16*4+6*18 =434g
the % of mass lost was 585-535/585 =0.0855

if youmultiply by 434, you find 37 (so, i suppose that 2 molecules of water were gone
UO(C2O4) ,4 H2O

2)