Question

In a laboratory experiment, when 35.0 g Mg reacted in excess O2, the percent yield of MgO was 90.0%. What was the actual yield of that experiment?

Answer 1

Answer:

Actual yield = 54 g      

Explanation:

Given data:

Mass of magnesium = 35.0 g

Percent yield = 90.0%

Actual yield = ?

Solution:

Chemical equation:

2Mg + O₂  →  2MgO

Number of moles of Mg:

Number of moles = mass/ molar mass

Number of moles = 35.0 g/ 24 g/mol

Number of moles = 1.5 mol

Now we will compare the moles of Mg and O.

                 Mg       :         MgO

                  2         :          2

                  1.5       :       1.5 mol

Mass of MgO: (theoretical yield)

Mass = number of moles × molar mass

Mass = 1.5 mol × 40 g/mol

Mass = 60 g

Percent yield = (actual yield / theoretical yield ) ×100

90.0 % = (actual yield / 60 g) ×100

0.9 = actual yield / 60 g

Actual yield = 0.9 × 60 g  

Actual yield = 54 g