Question

How many moles of MgCl2 will be produced from 65.0g of Mg(OH)2 , assuming HCl is available in excess

Answer 1

Answer:

1.12 moles of MgCl₂

Explanation:

Given parameters:

Mass of Mg(OH)₂  = 65g

Unknown:

Number of moles of MgCl₂ = ?

Solution:

To solve this problem, obtain a balanced reaction equation first;

           Mg(OH)₂  +   2HCl    →    MgCl₂   +   2H₂O

From the reaction above, this is a typical neutralization process in which an acid reacts with a base to produce salt and water only.

Let's proceed; the reactant in excess is the HCl, acid. The other reactant is the  Mg(OH)₂ and it must be the limiting reactant. A limiting reactant is one that is given in short supply and determines the extent of the reaction.

Find the number of moles of Mg(OH)₂;

   Number of moles  = $\frac{mass}{molar mass}$

     Molar mass of  Mg(OH)₂ = 24 + 2(16 + 1)  = 58g/mol

  Number of moles  = $\frac{65}{58}$    = 1.12moles

The balanced reaction equation shows that;

               1 mole of  Mg(OH)₂ gives 1 mole of MgCl₂

            1.12 mole of Mg(OH)₂ will produce 1.12 moles of MgCl₂