Answer:
Cu₂O.
Step-by-step explanation:
copper = 7.298
copper oxide = 8.217
oxygen in copper oxide = .919 g
7.298 g of copper = 7.298 / 63.5 mole of copper
= .1149 mole of copper
.919 g of oxygen = .919 / 16 mole of oxygen
= .0574 mole of oxygen
ratio of mole of copper and oxygen
= .1149 / .0574 = 2
formula of copper oxide = Cu₂O.