Chapter U4.2, Problem 4E

(a)

Interpretation Introduction

Interpretation: The chemical equation for the dissolution of sodium chloride in water needs to be written.

Concept Introduction: A chemical change can be defined as the conversion of one substance to another by making and breaking of chemical bonds.

Reactant molecules involve in chemical reaction and form new products. Chemical reactions can be classified as synthesis reaction, decomposition reaction, Redox reaction, displacement reactions, etc.

A chemical reaction can be represented as chemical equation which involves the chemical symbols of reactant and products.

Answer to Problem 4E

  ${\text{NaCl}}_{\text{(s) }}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l) }}\stackrel{}{\to }{\text{Na}}_{\text{(aq)}}^{\text{+}}{\text{+ Cl}}_{\text{(aq)}}^{\text{-}}$

Explanation of Solution

Solid sodium chloride is an ionic compound and soluble in water. It dissolves in water and forms ions in aqueous solution. It is also called as dissolution process.

Two ions; ${\text{Na}}_{\text{(aq)}}^{\text{+}}$ and ${\text{Cl}}_{\text{(aq)}}^{\text{-}}$ are formed during the reaction and the chemical equation can be written as:

  ${\text{NaCl}}_{\text{(s) }}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l) }}\stackrel{}{\to }{\text{Na}}_{\text{(aq)}}^{\text{+}}{\text{+ Cl}}_{\text{(aq)}}^{\text{-}}$

(b)

Interpretation Introduction

Interpretation: The chemical equation for the conversion of magnesium sulfide to solid magnesium and sulfur gas needs to be written.

Concept Introduction: A chemical change can be defined as the conversion of one substance to another by making and breaking of chemical bonds.

Reactant molecules involve in chemical reaction and form new products. Chemical reactions can be classified as synthesis reaction, decomposition reaction, Redox reaction, displacement reactions, etc.

A chemical reaction can be represented as chemical equation which involves the chemical symbols of reactant and products.

Answer to Problem 4E

  ${\text{MgS}}_{\text{(s) }}\stackrel{\Delta }{\to }{\text{Mg}}_{\text{(s)}}^{}{\text{+ S}}_{\text{(g)}}^{}$

Explanation of Solution

The conversion of magnesium sulfide to solid magnesium and sulfur gas is a thermal decomposition reaction.

In this reaction magnesium sulfide decomposes at high temperature to solid Mg and sulfur gas. The chemical equation can be written as:

  ${\text{MgS}}_{\text{(s) }}\stackrel{\Delta }{\to }{\text{Mg}}_{\text{(s)}}^{}{\text{+ S}}_{\text{(g)}}^{}$

(c)

Interpretation Introduction

Interpretation: The chemical equation for the formation of titanium dioxide by the reaction of titanium and oxygen gas while heating needs to be written.

Concept Introduction: A chemical change can be defined as the conversion of one substance to another by making and breaking of chemical bonds.

Reactant molecules involve in chemical reaction and form new products. Chemical reactions can be classified as synthesis reaction, decomposition reaction, Redox reaction, displacement reactions, etc.

A chemical reaction can be represented as chemical equation which involves the chemical symbols of reactant and products.

Answer to Problem 4E

  ${\text{Ti}}_{\text{(s) }}{\text{+O}}_{\text{2(g) }}\stackrel{\Delta }{\to }{\text{TiO}}_{\text{2(s) }}$

Explanation of Solution

The heating of solid titanium with oxygen gas results the formation of titanium dioxide. It is an example of synthesis or combination reaction as two reactant molecules combine to form one product.

The chemical formula of titanium dioxide is TiO₂ therefore the balance chemical reaction equation must be:

  ${\text{Ti}}_{\text{(s) }}{\text{+O}}_{\text{2(g) }}\stackrel{\Delta }{\to }{\text{TiO}}_{\text{2(s) }}$