A 7.298 g sample of copper reacts with oxygen, forming a copper oxide. The final mass of the copper oxide is 8.217 g. What is the formula of the copper oxide

Cu2O

Explanation:

We get mass of Cu and O in copper oxide.

Cu = copper

O = Oxygen

Cu = 7.298g

Then the mass of o is given as

CuO - Cu

= 8.217 - 7.298

= 0.919g

Then we get the number of moles

n = m/M

m = mass

M = molar mass

M of Cu = 63.55g/mol

M of oxygen = 16g/mol

n(copper) = 7.298/63.55

= 0.1148mol

n(oxygen) = 0.919/16g

= 0.0574mol

From here we get the molar ratio

n(copper)/n(oxygen)

= 0.1148/0.0574

= 2/1

Cu:O = 2:1

Cu2O is therefore the formula of copper Oxide

c. 75.7

i think that is the right