Question

Mg + O2 ——> 2MgO

Using the above balanced chemical equation, if a 0.23 g strip of magnesium is completely reacted….

​a. How many grams of oxygen would be required to complete the reaction?

​b. How many grams of magnesium oxide would be formed? Note that this is

called the theoretical yield of a reaction…in other words, based on a

calculation, how much of a given product is theoretically possible.

Answer 1

Obtain,

Molar mass of Magnesium = 24.305 g/mol

Molar mass of O₂ = 31.998 g/mol

Molar mass of MgO = 40.304 g/mol

For the balanced reaction,

1 Mg + 1 O₂2 MgO

a.

Moles of Mg in 0.23 g ,

= Mass of Mg/Molar mass of Mg

= ( 0.23 g)/(24.305 g/mol)

= 0.00946 moles of Mg

From the above reaction,1 mole of Mg reacts with 1 mole of O₂,

So 0.00946 moles of Mg will react with 0.00946 moles of O₂

Mass of O₂ in 0.00946 moles

= Moles of O₂ × Molar mass of O₂

= (0.00946 moles) × (31.998 g/mol)

= 0.303 g of O₂

b.

From the balanced reaction ,1 mole of Mg reacts with 1 mole of O₂ to form 2 moles of MgO,

So 0.00946 moles of Mg will react with 0.00946 moles of O₂to form ( 2 × 0.00946 = 0.01892) 0.01892 moles of MgO

So theoretical mass of MgO in 0.01892 moles of MgO,

= Moles of MgO × Molar mass of MgO

= (0.01892 moles) × (40.304 g/mol)

= 0.763 g of MgO