Question

magnesium burns in air with a dazzling brilliance to produce magnesium oxide: 2 mg(s) + o₂(g) → 2 mgo(s) when 5.50 g of magnesium burns, the theoretical yield of magnesium oxide is ______ g. 0.226 18.2 4.56 5.50 9.12

Explanation:

Step1: Calculate moles of Mg

The molar mass of Mg is approximately 24.31 g/mol. The number of moles of Mg, $n_{Mg}=\frac{m}{M}=\frac{5.50\ g}{24.31\ g/mol}\approx0.226\ mol$.

Step2: Determine mole - ratio

From the balanced chemical equation $2Mg(s)+O_2(g)\to2MgO(s)$, the mole - ratio of Mg to MgO is 1:1. So, the number of moles of MgO produced, $n_{MgO}=n_{Mg} = 0.226\ mol$.

Step3: Calculate mass of MgO

The molar mass of MgO is $M_{MgO}=24.31\ g/mol + 16.00\ g/mol=40.31\ g/mol$. The mass of MgO, $m_{MgO}=n_{MgO}\times M_{MgO}=0.226\ mol\times40.31\ g/mol\approx9.12\ g$.

Answer:

E. 9.12