If the arsenic is 76% and oxygen is 24% how would I calculate the chemical composition of of the oc=xide of arsenic that has been formed?

Question

Divide 76 by the atomic weight of As (which is 74.92) and 24 by the atomic weight of O (which is 16.00). The two new numbers that you get will be in the ratio of As atoms to O atoms. That ratio is approximately 1 to 1.5, which is the same as 2 parts As to 3 parts O.

Take a 100 g sample.
that gives you 76 g As and 24 g O.

Determine mols.
76/atomic mass As = ??
24/16 = mols O = ??

Now make the smaller number 1(by dividing by itself), then divide the other number of that number also.
That will give you the subscripts. Post your work if you need further assistance.

So would the chemical composition be As203

yes