A student heats a sample of copper powder in an open crucible. The copper reacts with oxygen gas from the air to produce copper(II) oxide:
copper+oxygen→copper(II) oxide \text{copper} + \text{oxygen} \rightarrow \text{copper(II) oxide} copper+oxygen→copper(II) oxideThe mass of the copper powder before heating is 12.70 g. After the reaction is complete, the mass of the copper(II) oxide formed is 15.90 g.
According to the law of conservation of mass, what mass of oxygen gas reacted with the copper?
3.20 g3.20\text{ g}3.20 g
1.60 g1.60\text{ g}1.60 g
15.90 g15.90\text{ g}15.90 g
28.60 g28.60\text{ g}28.60 g