Question

What will happen if you overheat the copper in your evaporating dish and how will this affect your determination of the moles of copper in the empirical formula?

A.The copper will not evaporate, so we don't have to worry about overheating; no effect on the number of moles

B.Copper will react with oxygen in the air; the moles of copper will be too low

C.Copper will react with oxygen in the air; the moles of copper will be too high

D.The copper will melt and we will not be able to get it out of our dish; no effect on the moles of copper though

Answer 1

Answer: C. Copper will react with oxygen in the air; the moles of copper will be too high

we know moles = mass of substance / molar mass of substance

in any case mass of substance increases then automatically calculated moles are also increases.

Cu +1/2 O₂ --> CuO

instead of copper mass we are calculating copper oxide mass, CuO mass is higher than Cu. Additional mass from oxygen increases actual copper mass.

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