Posted by Cory on .
Vanadium forms four different oxides in which the percent by mass of vanadium is respectively 76%, 68%, 61%, and 56%.
Find the formula of the first oxide.
How would I go about doing this? I tried to use my book but there are no examples of this question. Thanks!

chemistry 
DrBob222,
76% V so it must be 10076=24% oxygen since it is vanadium oxide.
So we take 100 g sample which gives us
76 g V and
24 g O
Convert to mols.
moles V = 76/atomic mass V.
moles O = 24/atomic mass O.
Now obtain the ratio of these two so that they are small whole numbers. The easiest way to do that is to divide the smaller number by itself to obtain 1.000, then divide the other one by that same small number.
That should give you the formula.
Post your work if you get stuck.