Empirical Formula

Question

A 1.56g sample of copper reacts with oxygen to form 1.95g of the metal oxide. 

What are the answers to step 1 (to 3 sig figs)?



mol O = 

 mol Cu = 

 

Answer 1

Cu +O2→Cu_xO_y

1.56g 1.95g

mass Cu_xO_y=mass Cu+mass O

mass O=mass Cu_xO_y - mass Cu

mass O=1.95g Cu_xO_y - 1.56 g Cu

mass O=0.39g O

convert to moles with molar mass

mol O

use molar mass

0.39gO/16=0.024375 mol

3 sig figs = 0.0244 mol

mol Cu

use molar mass

1.56gCu/63.546g=0.0245mol Cu

3 sig figs=0.0245 mol

Empirical formula should be CuO