Chapter 11, Problem 53A

Antacids Magnesium hydroxide is an ingredient in some antacids. Antacids react with excess hydrochloric acid in the stomach to relieve indigestion.

   $\text{\_\_Mg}{\left(\text{OH}\right)}_{\text{2}}\text{+\_\_HCl}\to {\text{\_\_MgCl}}_2{\text{+\_\_H}}_{\text{2}}\text{O}$

a. Balance the reaction of $\text{Mg}{\left(\text{OH}\right)}_{\text{2}}$ with HCI.

b. Write the mole ratio that would be used to determine the number of moles of ${\text{MgCl}}_2$ produced when HCI reacts with $\text{Mg}{\left(\text{OH}\right)}_{\text{2}}$ .

Interpretation Introduction

Interpretation:

The balance chemical equation for the reaction of magnesium hydroxide with hydrochloric acid needs to be determined.

Concept introduction:

The mole concept provides the relation between moles, mass and molar mass. The mathematical expression of mole concept can be written as:

$\text{Mole =}\frac{\text{Mass}}{\text{Molar mass}}$

1 mole of any substance contains $\text{6}\text{.022 }\times {\text{ 10}}^{\text{23}}$ number of particles or atoms or molecules.

Answer to Problem 53A

${\text{Mg(OH)}}_{\text{2}}{}_{\text{(s)}}{\text{+ 2 HCl}}_{\text{(aq)}}\stackrel{}{\to }{\text{ MgCl}}_{\text{2}}{}_{\text{(aq)}}{\text{+ 2 H}}_{\text{2}}{\text{O}}_{\text{(l)}}$

Explanation of Solution

The reaction of reaction of magnesium hydroxide with hydrochloric acid produces the magnesium chloride with water. The chemical formula of reactant and products are:

Magnesium hydroxide = ${\text{Mg(OH)}}_{\text{2}}$

Hydrochloric acid = HCl

Magnesium chloride = ${\text{MgCl}}_{\text{2}}$

Water = ${\text{H}}_{\text{2}}\text{O}$

Thus, the balance chemical equation must be:

${\text{Mg(OH)}}_{\text{2}}{}_{\text{(s)}}{\text{+ 2 HCl}}_{\text{(aq)}}\stackrel{}{\to }{\text{ MgCl}}_{\text{2}}{}_{\text{(aq)}}{\text{+ 2 H}}_{\text{2}}{\text{O}}_{\text{(l)}}$

Interpretation Introduction

(b)

Interpretation:

The mole ratio to determine the number of moles of ${\text{MgCl}}_{\text{2}}$ produced by the reaction of HCl with ${\text{Mg(OH)}}_{\text{2}}$ needs to be determined.

Concept introduction:

A chemical reaction involves the conversion of certain molecules (reactant) to new substance (product) by bond breaking and making. One of the reactants, which is present in limited amount and determines the amount of product is known as limiting reactant. Whereas another reactant is known as excess reactant.

Answer to Problem 53A

$\begin{array}{l}{\text{Mg(OH)}}_{\text{2}}{}_{\text{(s)}}{\text{+ 2 HCl}}_{\text{(aq)}}\stackrel{}{\to }{\text{ MgCl}}_{\text{2}}{}_{\text{(aq)}}{\text{+ 2 H}}_{\text{2}}{\text{O}}_{\text{(l)}}\\ \frac{{\text{1 moles MgCl}}_{\text{2}}{}_{\text{(aq)}}}{{\text{1 moles Mg(OH)}}_{\text{2}}{}_{\text{(s)}}}\text{ = }\frac{{\text{1 moles MgCl}}_{\text{2}}{}_{\text{(aq)}}}{{\text{2 moles HCl}}_{\text{(aq)}}}\end{array}$

Explanation of Solution

The balance chemical equation for the reaction of magnesium hydroxide with hydrochloric acid can write as:

${\text{Mg(OH)}}_{\text{2}}{}_{\text{(s)}}{\text{+ 2 HCl}}_{\text{(aq)}}\stackrel{}{\to }{\text{ MgCl}}_{\text{2}}{}_{\text{(aq)}}{\text{+ 2 H}}_{\text{2}}{\text{O}}_{\text{(l)}}$

The mole ratio relates the moles of reactant with other reactant and product molecules in the balance chemical equation. Thus, one mole ratio relates with other mole ratio. The mole ratio for ${\text{MgCl}}_{\text{2}}$ production by the reaction of HCl with ${\text{Mg(OH)}}_{\text{2}}$.

$\begin{array}{l}{\text{Mg(OH)}}_{\text{2}}{}_{\text{(s)}}{\text{+ 2 HCl}}_{\text{(aq)}}\stackrel{}{\to }{\text{ MgCl}}_{\text{2}}{}_{\text{(aq)}}{\text{+ 2 H}}_{\text{2}}{\text{O}}_{\text{(l)}}\\ \frac{{\text{1 moles MgCl}}_{\text{2}}{}_{\text{(aq)}}}{{\text{1 moles Mg(OH)}}_{\text{2}}{}_{\text{(s)}}}\text{ = }\frac{{\text{1 moles MgCl}}_{\text{2}}{}_{\text{(aq)}}}{{\text{2 moles HCl}}_{\text{(aq)}}}\end{array}$