Question

Magnesium burns in air with a dazzling brilliance to produce magnesium oxide:

2Mg(s)+O₂(g)→2MgO(s)
when 4.00 g of magnesium burns, the theoretical yield of magnesium oxide is ________ g.
A. 4.00
B. 0.165
C. 3.32
D. 13.3
E. 6.63

Answer 1

e.6.63 g.

Using stoichiometry based on the molar masses of magnesium and magnesium oxide, the theoretical yield of MgO when 4.00 g of magnesium burns is found to be

Step-by-step explanation:

When 4.00 g of magnesium burns, the theoretical yield of magnesium oxide is calculated by using the stoichiometry of the reaction 2Mg(s) + O₂(g) → 2MgO(s). To find the theoretical yield, we first need to determine the molar mass of magnesium (Mg) and magnesium oxide (MgO), which are approximately 24.31 g/mol and 40.31 g/mol, respectively.

Next, we calculate the number of moles of magnesium in 4.00 g:

4.00 g Mg * (1 mol Mg / 24.31 g Mg) ≈ 0.1646 moles Mg

Since the reaction shows a 1:1 mole ratio between Mg and MgO, this means 0.1646 moles of magnesium will yield 0.1646 moles of MgO. Finally, we calculate the mass of the MgO produced:

0.1646 moles MgO * (40.31 g MgO / 1 mol MgO) ≈ 6.63g MgO

The correct answer is therefore E. 6.63g.