Question

12g of magnesium ribbon was heated in a crucible. At the end of the reaction 20g of magnesium oxide had been produced. What mass of oxygen had reacted with the magnesium?

Answer 1

Answer: 16 g of $O_{2}$ reacted with the magnesium

Explanation:

from the equation of reaction: 2Mg + $O_{2}$→$2MgO$

48g of Mg requires 32g of O2 to yield 80g of MgO

That is :

    48 : 32 : 80

Hence 12 : x: 32

xg of O2  =$\frac{12(32)}{48}$

= 16 g of $O_{2}$

Therefore:

16 g of $O_{2}$ reacted with the magnesium