Question

An oxide of copper contains 2.118 g of copper and 0.2666 g of oxygen. Another oxide of copper contains the same mass of copper but 0.5332 g of copper. What are the empirical formulas of the oxides?

Answer 1

Oxide 1

Cu+O-----> Oxide 1

Our job is to calculate the ratio of the moles of each element.

Moles of Cu =2.118 g Cul× 1 mol Cu /63.55 g Cu =0.016 66 mol O

Moles of O= 0.2666 g O × 1 mol O /16.00 g O= 0.016 66 mol O

To get the molar ratio, we divide each number of moles by the smaller number ( 0.01 666 ).

From here on, I like to summarize the calculations in a table.

Element     Mass/g      Moles   Ratio   Integers

Cu             2.118       0.033 28  1.997      2

O               0.2666 l  0.016 66    1            1

The empirical formula of Oxide 1 is  Cu 2 O .

Do the same for Oxide 2

the empirical formula of Oxide 2 is CuO ratio is 1:1