Question

How do I calculate the mas of oxygen that combines with one mol of arsenic atoms to form the oxide of arsenic?

How would I use this answer to obtain the empirical formula of the oxide?

The formula for the most common form of arsenic oxids is As2O3.

Write down the balanced equation for the reaction, with O2 as the other reactant.

Figure out the number of moles of O2 required per mole of As.

Multiply the number of moles of O2 by 32 grams/mole, fo get tha answer.