Question

When 1.375 g of copper (II) oxide is reduced on heating in a current of hydrogen, the weight of copper remaining after the reaction is complete is 1.098 g. What is the percent composition of oxygen?

Answer 1

20.11% of oxygen

Step-by-step explanation:

The reaction is:

2CuO ⇒ 2Cu + O2

If you have an initial amoung of a sample, thi may be have impurities, so you have to start from products to know what you had at the begining.

to make a relation between reagents and products you need to change the mass to mol, then you can relate them with the molar ratio.

`1,098gCu x (1mol Cu)/(63.546g Cu) x (2mol CuO)/(2molCu) x (1mol O)/(1molCuO) x (16gO)/(1molO) = 0,276gO`

Now you have the initial amount of oxygen, to convert to percent you must divide the mass of oxygen between the mass of the sample and multiply by 100

`percent composition of O = (0.276gO)/(1.375g sample) *100 = 20.11`