1.2 g of copper powder on heatinf gave 6.0 g of copper oxide. In another experiment, copper oxide contained 20% oxygen. Show that these results illustrate the law of constant proportion.
2Cu + O2 → 2CuO
2moles of CuO is given by = 1 mole of oxygen.
no. of moles of CuO in 6 g =6/79 moles
6/79 moles of CuO will give = (6/79)×(1/2)=0.037 moles
Mass of 0.037 moles of Oxygen= 0.037×32=1.184 g
Thus % of OXYGEN in CuO = (1.184/6)×100=20 % OF OXYGEN