Question

1. 2Mg + O₂ → 2MgO How many moles of MgO form if 6mol of oxygen react? *

Answer 1

Answer:

12 moles of MgO

1.8 moles of O₂

5.5 moles of Mg

Explanation:

These questions are all related and they involve comparing the number of moles of reactant to products.

Here we use molar relationship because they express what happens in a reaction much more better.

Problem 1:

                     2Mg    +     O₂     →    2MgO

We work from the known to the unknown;

              The known is oxygen gas;  which is 6moles

                       Unknown is MgO;

                    1 mole of O₂ produced 2 mole of MgO

                    6 moles of O₂ will produce  (6 x 2) moles of MgO

                                                                    = 12 moles of MgO

Problem 2:

               2Mg    +     O₂     →    2MgO

            Known;  3.6 moles of Magnesium

            Unknown;  number of moles of oxygen;

            2 moles of Mg reacted with 1 mole of O₂

          3.6 moles of Mg will react with   $\frac{3.6}{2}$   = 1.8 moles of O₂

Problem 3:

             2Mg    +     O₂     →    2MgO

           Known: number of of moles of MgO  = 5.5moles

           Unknown: number of moles of Mg = ?

          2 moles of MgO will be produced from 2 moles of Mg

         5.5 moles of MgO will be produced from $\frac{5.5 x 2}{2}$   = 5.5 moles of Mg