Chapter 6, Problem 6.23P

(a)

Interpretation Introduction

Interpretation:

The chemical formula and balanced chemical equation of sodium sulphide from sodium and sulphur has to be written.

Concept Introduction:

1. 1) The chemical formula of binary compound from a pair of its constituent ion has to be written.
2. 2) The coefficients of the ions with the magnitude of the charge on each of the ions have to be crossed multiplied.  This is done to neutralize charge on the binary compound.
3. 3) The oxidation state of the metal is written in roman numbers in the brackets

Answer to Problem 6.23P

The chemical formula is ${\text{Na}}_{\left(\text{s}\right)}{\text{+S}}_{\text{8(s)}}\stackrel{}{\to }{\text{Na}}_{\text{2}}{\text{S}}_{\left(\text{s}\right)}\text{.}$

The balanced chemical equation is ${\text{16Na}}_{\left(\text{s}\right)}{\text{+S}}_{\text{8}\left(\text{s}\right)}\stackrel{}{\to }{\text{8Na}}_{\text{2}}{\text{S}}_{\left(\text{s}\right)}\text{.}$

Explanation of Solution

Sodium has a monopositive charge $\left({\text{Na}}^{\text{+}}\right)$ and sulphur belongs to the group 16 and forms a dinegative anion $\left({\text{S}}^{\text{2-}}\right)$ known as sulphide.  The chemical formula is,

  ${\text{Na}}^{+}{\text{+S}}^{2-}\stackrel{}{\to }{\text{Na}}_{\text{2}}\text{S}$

But sulphur in nature exists as ${\text{S}}_{\text{8}}\text{.}$  The equation becomes,

  ${\text{Na}}_{\left(\text{s}\right)}{\text{+S}}_{\text{8(s)}}\stackrel{}{\to }{\text{Na}}_{\text{2}}{\text{S}}_{\left(\text{s}\right)}$

Sixteen moles of sodium are required in the reactant side and eight moles of sodium sulphide are required in the product side to make the equation a balanced one.  The balanced chemical equation is,

  ${\text{16Na}}_{\left(\text{s}\right)}{\text{+S}}_{\text{8}\left(\text{s}\right)}\stackrel{}{\to }{\text{8Na}}_{\text{2}}{\text{S}}_{\left(\text{s}\right)}$

(b)

Interpretation Introduction

Interpretation:

The chemical formula and balanced chemical equation of calcium bromide from calcium and bromine has to be written.

Concept Introduction:

Refer to part (a).

Answer to Problem 6.23P

The chemical formula is ${\text{Ca}}_{\left(\text{s}\right)}{\text{+Br}}_{\text{2(l)}}\stackrel{}{\to }{\text{CaBr}}_{\text{2(s)}}.$

The balanced chemical equation is ${\text{Ca}}_{\left(\text{s}\right)}{\text{+Br}}_{\text{2(l)}}\stackrel{}{\to }{\text{CaBr}}_{\text{2(s)}}.$

Explanation of Solution

Calcium has a dipositive charge $\left({\text{Ca}}^{\text{2+}}\right)$ and bromine belongs to the group 17 and forms a mononegative anion $\left({\text{Br}}^{\text{-}}\right)$ known as bromide.  The chemical formula is,

  ${\text{Ca}}^{\text{2+}}{\text{+Br}}^{\text{-}}\stackrel{}{\to }{\text{CaBr}}_{\text{2}}$

But bromine in nature exists as ${\text{Br}}_{\text{2}}\text{.}$  The equation becomes,

  ${\text{Ca}}_{\left(\text{s}\right)}{\text{+Br}}_{\text{2(l)}}\stackrel{}{\to }{\text{CaBr}}_{\text{2}\left(\text{s}\right)}$

The above reaction is self-balanced.

(c)

Interpretation Introduction

Interpretation:

The chemical formula and balanced chemical equation of barium oxide from barium and oxygen has to be written.

Concept Introduction:

Refer to part (a).

Answer to Problem 6.23P

The chemical formula is ${\text{Ba}}_{\left(\text{s}\right)}{\text{+O}}_{\text{2(g)}}\stackrel{}{\to }{\text{BaO}}_{\left(\text{s}\right)}\text{.}$

The balanced chemical equation is ${\text{2Ba}}_{\left(\text{s}\right)}{\text{+O}}_{\text{2(g)}}\stackrel{}{\to }{\text{2BaO}}_{\left(\text{s}\right)}\text{.}$

Explanation of Solution

Barium has a dipositive charge $\left({\text{Ba}}^{\text{2+}}\right)$ and oxygen belongs to the group 16 and forms a dinegative anion $\left({\text{O}}^{\text{2-}}\right)$ known as oxide.  The chemical formula is,

  ${\text{Ba}}^{\text{2+}}{\text{+O}}^{\text{2-}}\stackrel{}{\to }\text{BaO}$

But oxygen in nature exists as ${\text{O}}_{\text{2}}\text{.}$  The equation becomes,

  ${\text{Ba}}_{\left(\text{s}\right)}{\text{+O}}_{\text{2(g)}}\stackrel{}{\to }{\text{BaO}}_{\left(\text{s}\right)}$

Two moles of barium are required in the reactant side and two moles of barium oxide are required in the product side to make the equation a balance one.  The balanced chemical equation is,

  ${\text{2Ba}}_{\left(\text{s}\right)}{\text{+O}}_{\text{2(g)}}\stackrel{}{\to }{\text{2BaO}}_{\left(\text{s}\right)}$

(d)

Interpretation Introduction

Interpretation:

The chemical formula and balanced chemical equation of sulphur trioxide from sulphur dioxide and oxygen has to be written.

Concept Introduction:

Refer to part (a).

Answer to Problem 6.23P

The chemical formula is ${\text{SO}}_{\text{2(g)}}{\text{+O}}_{\text{2(g)}}\stackrel{}{\to }{\text{SO}}_{\text{3(g)}}.$

The balanced chemical equation is ${\text{2SO}}_{\text{2(g)}}{\text{+O}}_{\text{2(g)}}\stackrel{}{\to }{\text{2SO}}_{\text{3(g)}}.$

Explanation of Solution

Sulphur dioxide and oxygen exists as gas in nature.  They react with each other to form sulphur trioxide.  The chemical reaction is written as,

  ${\text{SO}}_{\text{2(g)}}{\text{+O}}_{\text{2(g)}}\stackrel{}{\to }{\text{SO}}_{\text{3(g)}}$

Two moles of sulphur dioxide are required in the reactant side and two moles of sulphur trioxide are required in the product side to make the reaction a balanced one.  The balanced equation is,

  ${\text{2SO}}_{\text{2(g)}}{\text{+O}}_{\text{2(g)}}\stackrel{}{\to }{\text{2SO}}_{\text{3(g)}}$