Chapter F, Problem H.7E

(a)

Interpretation Introduction

Interpretation:

Balanced chemical equation has to be written for the reaction of calcium metal with water to produce calcium hydroxide and hydrogen gas.

Concept Introduction:

Chemical equation is a short form representation of a chemical reaction with all the required conditions necessary for the reaction to take place.  As the atoms are neither created nor destroyed in a chemical reaction, the number of atoms of same element has to be equal on both sides of the equation.  This is known as balanced chemical equation.  Coefficients can be changed but not the subscript.

Answer to Problem H.7E

Balanced chemical equation is $\text{Ca}(s)+2{\text{H}}_{\text{2}}\text{O}(l)\to {\text{Ca(OH)}}_{\text{2}}(aq)+{\text{H}}_{\text{2}}(g)$.

Explanation of Solution

The reaction given is calcium metal reacts with water to produce aqueous calcium hydroxide and hydrogen gas.  The skeletal equation for the reaction can be represented as shown below;

    $\text{Ca}(s)+{\text{H}}_{\text{2}}\text{O}(l)\to {\text{Ca(OH)}}_{\text{2}}(aq)+{\text{H}}_{\text{2}}(g)$

Balancing oxygen atoms:  In the reactant side, there is only one oxygen atom while on the product side, there are two oxygen atoms.  Adding coefficient $2$ before ${\text{H}}_{\text{2}}\text{O}$ balances the oxygen atoms on both sides of the equation.  This step balances the other atoms also.  Therefore, the balanced chemical equation can be written as follows;

    $\text{Ca}(s)+2{\text{H}}_{\text{2}}\text{O}(l)\to {\text{Ca(OH)}}_{\text{2}}(aq)+{\text{H}}_{\text{2}}(g)$

(b)

Interpretation Introduction

Interpretation:

Balanced chemical equation has to be written for the reaction of sodium oxide with water to produce sodium hydroxide.

Concept Introduction:

Refer part (a).

Answer to Problem H.7E

Balanced chemical equation is ${\text{Na}}_{\text{2}}\text{O}(s)+{\text{H}}_{\text{2}}\text{O}(l)\to 2\text{NaOH}(aq)$.

Explanation of Solution

The reaction given is sodium oxide reacts with water to produce sodium hydroxide.  The skeletal equation for the reaction can be represented as shown below;

    ${\text{Na}}_{\text{2}}\text{O}(s)+{\text{H}}_{\text{2}}\text{O}(l)\to \text{NaOH}(aq)$

Balancing oxygen atoms:  In the reactant side, there are two oxygen atoms while on the product side, there is only one oxygen atom.  Adding coefficient $2$ before $\text{NaOH}$ balances the oxygen atoms on both sides of the equation.  This step balances the other atoms also.  Therefore, the balanced chemical equation can be written as follows;

    ${\text{Na}}_{\text{2}}\text{O}(s)+{\text{H}}_{\text{2}}\text{O}(l)\to 2\text{NaOH}(aq)$

(c)

Interpretation Introduction

Interpretation:

Balanced chemical equation has to be written for the reaction of magnesium metal with nitrogen to produce magnesium nitride.

Concept Introduction:

Refer part (a).

Answer to Problem H.7E

Balanced chemical equation is $\text{3Mg}(s)+{\text{N}}_{\text{2}}(g)\to {\text{Mg}}_{\text{3}}{\text{N}}_{\text{2}}(s)$.

Explanation of Solution

The reaction given is magnesium reacts with nitrogen to produce magnesium nitride.  The skeletal equation for the reaction can be represented as shown below;

    $\text{Mg}(s)+{\text{N}}_{\text{2}}(g)\to {\text{Mg}}_{\text{3}}{\text{N}}_{\text{2}}(s)$

Balancing magnesium atoms:  In the reactant side, there is one magnesium atom while on the product side, there are three magnesium atoms.  Adding coefficient $3$ before $\text{Mg}$ balances the magnesium atoms on both sides of the equation.  This step balances the other atoms also.  Therefore, the balanced chemical equation can be written as follows;

    $\text{3Mg}(s)+{\text{N}}_{\text{2}}(g)\to {\text{Mg}}_{\text{3}}{\text{N}}_{\text{2}}(s)$

(d)

Interpretation Introduction

Interpretation:

Balanced chemical equation has to be written for the reaction of ammonia gas with oxygen to form gaseous water and nitrogen dioxide.

Concept Introduction:

Refer part (a).

Answer to Problem H.7E

Balanced chemical equation is ${\text{4NH}}_{\text{3}}(g)+7{\text{O}}_{\text{2}}(g)\underset{\text{Cu}}{\overset{\Delta }{\to }}{\text{6H}}_{\text{2}}\text{O}(g)+4{\text{NO}}_{\text{2}}(g)$.

Explanation of Solution

The reaction given is ammonia reacting with oxygen at high temperature to produce gaseous water and nitrogen dioxide.  The skeletal equation for the reaction can be represented as shown below;

    ${\text{NH}}_{\text{3}}(g)+{\text{O}}_{\text{2}}(g)\underset{\text{Cu}}{\overset{\Delta }{\to }}{\text{H}}_{\text{2}}\text{O}(g)+{\text{NO}}_{\text{2}}(g)$

Balancing hydrogen atoms:  In the reactant side, there are three hydrogen atoms while on the product side, there are two hydrogen atoms.  Adding coefficient $2$ before ${\text{NH}}_{\text{3}}$ and coefficient $3$ before ${\text{H}}_{\text{2}}\text{O}$ balances the hydrogen atoms on both sides of the equation.  Therefore, the chemical equation can be written as follows;

    ${\text{2NH}}_{\text{3}}(g)+{\text{O}}_{\text{2}}(g)\underset{\text{Cu}}{\overset{\Delta }{\to }}{\text{3H}}_{\text{2}}\text{O}(g)+{\text{NO}}_{\text{2}}(g)$

Balancing nitrogen atoms:  In the reactant side, there are two nitrogen atoms while on the product side, there is only one nitrogen atom.  Adding coefficient $2$ before ${\text{NO}}_{\text{2}}$ balances the nitrogen atoms on both sides of the equation.  Therefore, the chemical equation can be written as follows;

    ${\text{2NH}}_{\text{3}}(g)+{\text{O}}_{\text{2}}(g)\underset{\text{Cu}}{\overset{\Delta }{\to }}{\text{3H}}_{\text{2}}\text{O}(g)+2{\text{NO}}_{\text{2}}(g)$

Balancing oxygen atoms:  In the reactant side, there are two oxygen atoms while on the product side, there are seven oxygen atoms.  Adding coefficient $3.5$ before ${\text{O}}_{\text{2}}$ balances the oxygen atoms on both sides of the equation.  Therefore, the balanced chemical equation can be written as follows;

    ${\text{2NH}}_{\text{3}}(g)+3.5{\text{O}}_{\text{2}}(g)\underset{\text{Cu}}{\overset{\Delta }{\to }}{\text{3H}}_{\text{2}}\text{O}(g)+2{\text{NO}}_{\text{2}}(g)$

In order to obtain in whole numbers, the equation is multiplied by $2$.  Thus, the balanced chemical equation can be given as follows;

    ${\text{4NH}}_{\text{3}}(g)+7{\text{O}}_{\text{2}}(g)\underset{\text{Cu}}{\overset{\Delta }{\to }}{\text{6H}}_{\text{2}}\text{O}(g)+4{\text{NO}}_{\text{2}}(g)$