A student heats magnesium to produce magnesium oxide.

Question

A student heats magnesium to produce magnesium oxide.
the reaction is below:

Mg + O2 MgO

She starts wih 3.45 grams of magnesium and produces 5.65 grams of magnesium oxide. Calculate her theoretical yield of magnesium oxide with a stoichiometry calculation. Use 3.45 grams of magnesium as a starting point and determine how many grams she should have produced in the reaction if she was flawless in her procedure. Ensure the equation is balanced. After you calculate her theoretical yield, use it along with the experimental yield to calculate her % yield & percent error.

Answer 1

The balanced equation is 

 

2Mg + O₂ -> 2MgO

 

First find the number of moles of magnesium that are required to react with oxygen. To do that use the periodic table to determine the molecular weight of Mg.

 

MW of Mg = 24.31 g/mol

moles of Mg = 0.14192 = mol MgO   from the relation given in the chemical equation (2 mol Mg react to give 2 mol MgO)

 

MW of MgO = 40.31 g/mol

mass of MgO = 5.72 g = theoretical yield

 

The percent yield is   percent yield = (actual yield/theoretical yield)*100

the actual yield is 5.65 g and the theoretical yield is 5.72 g

 

percent yield = 98.8%

 

percent error is        percent error = |theoretical - experimental/theoretical|*100

 

percent error = 1.22%