Question

Magnesium metal reacts quantitatively with oxygen to give magnesium oxide, MgO. If 5.00g of Mg and %.00g of O2 are allowed to react, what weight of MgO is formed; and what weight of which reactant is left in excess?

Answer 1

2 Mg(s) + O₂(g) → 2 MgO(s)

Moles Mg $=\frac{5.00}{24.305}=0.206moles$

Mole ratio 2:2

Hence moles of MgO=0.206 moles

Mass of MgO=$0.206×40.30=8.3018grams$