Question

How many grams of magnesium oxide forms when 8.0g of magnesium are burned?

Answer 1

Magnesium burns with oxygen to give magnesium oxide based on the following reaction:
2Mg+O2 ........> 2MgO(s)+energy
From the periodic table:
molecular mass of magnesium = 24.3 grams
molecular mass of oxygen = 16 grams

From the reaction:
2 x 24.3 = 48.6 grams of magnesium are required to produce 2(24.3+16) = 80.6 grams of magnesium oxide.
We can know the amount of magnesium oxide produced from 8 grams of magnesium by simply doing cross multiplication as follows:
amount of magnesium oxide = (8 x 80.6) / 48.6 = 13.267 grams