Chapter 10, Problem 211A

Interpretation Introduction

Interpretation:

The balanced chemical equation for the reaction between magnesium metal and water to produce solid magnesium hydroxide and hydrogen gas should be determined.

Concept introduction:

Chemical equation is written in such a way that the symbolic representation of reaction represents the reaction taking place in the system. The reactants are written on the left-hand side and the products are written on the right-hand side of the equation and are separated by an arrow, two or more reactants and products are separated by “+”. The reactions for those the number of atoms of each element in the reactant and in the product, side are equal, such reactions are said to be a balanced chemical equation.

Answer to Problem 211A

${\text{Mg(s) + 2H}}_{\text{2}}\text{O(l) }\to \text{ Mg}{\left(\text{OH}\right)}_{\text{2}}{\text{(s) + H}}_{\text{2}}\text{(g)}$

Explanation of Solution

The elemental formula for magnesium is $\text{Mg}$, molecular formula for water is ${\text{H}}_{\text{2}}\text{O}$, for magnesium hydroxide is $\text{Mg}{\left(\text{OH}\right)}_2$ and for hydrogen is ${\text{H}}_{\text{2}}$.

The physical state of the reactants and products are shown by writing the symbols after each reactant and product in the reaction. The symbol “l” represents liquid, “aq” represents aqueous, “s” represents solid, and “g” represents gas.

The reaction between magnesium metal and water to produce solid magnesium hydroxide and hydrogen gas is written as:

${\text{Mg(s) + H}}_{\text{2}}\text{O(l) }\to \text{ Mg}{\left(\text{OH}\right)}_{\text{2}}{\text{(s) + H}}_{\text{2}}\text{(g)}$

This reaction is not balanced as the number of H and O atoms on the reactant side is 2 and 1 whereas in the product side is 4 and 2 respectively. So, in order to balance the reaction, coefficient 2 is written before ${\text{H}}_{\text{2}}\text{O(l)}$ in the reactant side. Hence, the balanced reaction is:

${\text{Mg(s) + 2H}}_{\text{2}}\text{O(l) }\to \text{ Mg}{\left(\text{OH}\right)}_{\text{2}}{\text{(s) + H}}_{\text{2}}\text{(g)}$

Interpretation Introduction

Interpretation:

The balanced chemical equation for the decomposition of dinitrogen tetroxide gas to nitrogen dioxide should be determined.

Concept introduction:

Chemical equation is written in such a way that the symbolic representation of reaction represents the reaction taking place in the system. The reactants are written on the left-hand side and the products are written on the right-hand side of the equation and are separated by an arrow, two or more reactants and products are separated by “+”. The reactions for those the number of atoms of each element in the reactant and in the product, side are equal, such reactions are said to be a balanced chemical equation.

Answer to Problem 211A

${\text{N}}_{\text{2}}{\text{O}}_4\text{(g) }\to {\text{ 2NO}}_{\text{2}}\text{(g)}$

Explanation of Solution

The molecular formula for dinitrogen tetroxide is ${\text{N}}_{\text{2}}{\text{O}}_4$ and for nitrogen dioxide is ${\text{NO}}_{\text{2}}$.

The physical state of the reactants and products are shown by writing the symbols after each reactant and product in the reaction. The symbol “l” represents liquid, “aq” represents aqueous, “s” represents solid, and “g” represents gas.

The reaction for the decomposition of dinitrogen tetroxide gas to nitrogen dioxide is written as:

${\text{N}}_{\text{2}}{\text{O}}_4\text{(g) }\to {\text{ NO}}_{\text{2}}\text{(g)}$

This reaction is not balanced as the number of N and O atoms on the reactant side is 2 and 4 whereas in the product side is 1 and 2 respectively. So, in order to balance the reaction, coefficient 2 is written before ${\text{NO}}_{\text{2}}$ in the product side. Hence, the balanced reaction is:

${\text{N}}_{\text{2}}{\text{O}}_4\text{(g) }\to {\text{ 2NO}}_{\text{2}}\text{(g)}$

Interpretation Introduction

Interpretation:

The balanced chemical equation for aqueous solutions of potassium hydroxide and sulfuric acid undergoing double replacement reaction should be determined.

Concept introduction:

Chemical equation is written in such a way that the symbolic representation of reaction represents the reaction taking place in the system. The reactants are written on the left-hand side and the products are written on the right-hand side of the equation and are separated by an arrow, two or more reactants and products are separated by “+”. The reactions for those the number of atoms of each element in the reactant and in the product, side are equal, such reactions are said to be a balanced chemical equation.

Answer to Problem 211A

${\text{H}}_{\text{2}}{\text{SO}}_4\text{(aq) + 2KOH(aq})\to {\text{K}}_{\text{2}}{\text{SO}}_4{\text{(aq) + 2H}}_{\text{2}}\text{O(l)}$

Explanation of Solution

The molecular formula for sulfuric acid is ${\text{H}}_{\text{2}}{\text{SO}}_4$ and for potassium hydroxide is $\text{KOH}$.

The physical state of the reactants and products are shown by writing the symbols after each reactant and product in the reaction. The symbol “l” represents liquid, “aq” represents aqueous, “s” represents solid, and “g” represents gas.

In double replacement reaction, the anions (or the cations) are exchanged between starting compounds and results in the formation of product.

The reaction for aqueous solutions of potassium hydroxide and sulfuric acid undergoing double replacement reaction is written as:

${\text{H}}_{\text{2}}{\text{SO}}_4\text{(aq) + KOH(aq})\to {\text{K}}_{\text{2}}{\text{SO}}_4{\text{(aq) + H}}_{\text{2}}\text{O(l)}$

This reaction is not balanced as the number of H and K atoms on the reactant side is 3 and 1 whereas in the product side is 2. So, in order to balance the reaction, coefficient 2 is written before $\text{KOH}$ in the reactant side and before ${\text{H}}_{\text{2}}\text{O}$ on the product side. Hence, the balanced reaction is:

${\text{H}}_{\text{2}}{\text{SO}}_4\text{(aq) + 2KOH(aq})\to {\text{K}}_{\text{2}}{\text{SO}}_4{\text{(aq) + 2H}}_{\text{2}}\text{O(l)}$