Chapter 8, Problem 28PE

(a)

Interpretation Introduction

Interpretation:

The reactants that will form $\text{Pb}\left(\text{s}\right)\text{+Ni}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)$ have to be given.  The equation has to be balanced and the type of reaction has to be classified.

Concept Introduction:

Combination reactions/Synthesis reactions:  In these reactions, the reactant combines to form a single product.  This type of reaction occurs between either two elements, an element and a compound or two compounds.  It is recognized easily because it involves two reactants and only a single product.

Example:  The product for the combination reaction of magnesium oxide and carbon dioxide is magnesium carbonate.  The completed equation is,

  $\text{MgO}\left(\text{s}\right){\text{+CO}}_{\text{2}}\left(\text{g}\right)\stackrel{}{\to }{\text{MgCO}}_{\text{3}}\left(\text{s}\right)$

Single displacement reactions:  A reaction where an element in a compound is replaced by another element is called single displacement reaction or a substitution reaction.  It generally involves between a dilute solution of an acid and a metal.

Example:  The product for the single displacement reaction of reaction of zinc and hydrogen bromide is zinc bromide and hydrogen.  The balanced reaction is,

  $\text{Zn}\left(\text{s}\right)\text{+2HBr}\left(\text{aq}\right)\stackrel{}{\to }{\text{ZnBr}}_{\text{2}}\left(\text{s}\right){\text{+H}}_{\text{2}}\left(\text{g}\right)$

Double displacement reactions:  This type of reactions occurs when the cation and the anions switch between two reactants to form new products.  In order for the reaction to occur, one of the products is usually a solid precipitate, a gas or a molecular compound.

Example:  The product of the reaction between nitric acid and calcium sulphide is gaseous hydrogen sulphide and calcium nitrate.  The completed equation is,

  $\text{CaS}\left(\text{s}\right){\text{+2HNO}}_{\text{3}}\left(\text{aq}\right)\stackrel{}{\to }\text{Ca}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right){\text{+H}}_{\text{2}}\text{S}\left(\text{g}\right)$

Decomposition reactions:  Decomposition reactions are the opposite of a combination reaction because decomposition reaction involves the breaking apart of a substance into simpler substances.  Such a reaction is easy to recognize because there is one reactant and more than one product.

Example:  The reaction of sodium chlorate to sodium chloride and oxygen is decomposition reaction.  The balanced reaction is,

  ${\text{2NaClO}}_{\text{3}}\left(\text{s}\right)\stackrel{}{\to }\text{2NaCl}\left(\text{s}\right){\text{+3O}}_{\text{2}}\left(\text{g}\right)$

Answer to Problem 28PE

The reactants that will form $\text{Pb}\left(\text{s}\right)\text{+Ni}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)$ are nickel and lead (II) nitrate.

The balanced reaction is,

  $\text{Ni}\left(\text{s}\right)\text{+Pb}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\stackrel{}{\to }\text{Pb}\left(\text{S}\right)\text{+Ni}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)$

The reaction is a single displacement reaction.

Explanation of Solution

The reactants that will react to form the products nickel (II) chloride and lead are nickel and lead (II) nitrate.  The chemical equation is written as,

  $\text{Ni}\left(\text{s}\right)\text{+Pb}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\stackrel{}{\to }\text{Pb}\left(\text{S}\right)\text{+Ni}{\left({\text{NO}}_{\text{3}}\right)}_{\text{2}}\left(\text{aq}\right)$

The above reaction is self-balanced.

The reaction of nickel with lead (II) nitrate is a single displacement reaction because nickel is more reactive than lead, so it will displace lead from lead (II) nitrate and forms nickel (II) nitrate and metallic lead.

(b)

Interpretation Introduction

Interpretation:

The reactants that will form $\text{Mg}{\left(\text{OH}\right)}_{\text{2}}\left(\text{s}\right)$ have to be given.  The equation has to be balanced and the type of reaction has to be classified.

Concept Introduction:

Refer to part (a).

Answer to Problem 28PE

The reactants that will form $\text{Mg}{\left(\text{OH}\right)}_{\text{2}}\left(\text{s}\right)$ are magnesium oxide and water.

The balanced reaction is,

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

The reaction is a synthesis/combination reaction.

Explanation of Solution

The reactants that will react to form the products magnesium hydroxide are magnesium oxide and water.  The chemical equation is written as,

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

The above reaction is self-balanced.

The reaction of magnesium oxide with water to form magnesium hydroxide is a synthesis reaction because two reactants are combined to form single product.

(c)

Interpretation Introduction

Interpretation:

The reactants that will form $\text{Hg}\left(\text{l}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)$ have to be given.  The equation has to be balanced and the type of reaction has to be classified.

Concept Introduction:

Refer to part (a).

Answer to Problem 28PE

The reactant that will form $\text{Hg}\left(\text{l}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)$ is mercury (II) oxide.

The balanced equation is,

  $\text{2HgO}\left(\text{s}\right)\stackrel{}{\to }\text{2Hg}\left(\text{l}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)$

The reaction is decomposition reaction.

Explanation of Solution

The reactant that will form the product $\text{Hg}\left(\text{l}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)$ is mercury (II) oxide.  The chemical equation is,

  $\text{HgO}\left(\text{s}\right)\stackrel{}{\to }\text{Hg}\left(\text{l}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)$

The above reaction is unbalanced.  The balanced equation is,

  $\text{2HgO}\left(\text{s}\right)\stackrel{}{\to }\text{2Hg}\left(\text{l}\right){\text{+O}}_{\text{2}}\left(\text{g}\right)$

The reaction of mercury (II) oxide to form mercury and oxygen is a decomposition reaction because a single reactant results in the formation of two products.

(d)

Interpretation Introduction

Interpretation:

The reactants that will form ${\text{PbCO}}_{\text{3}}\left(\text{s}\right){\text{+NH}}_{\text{4}}\text{Cl}\left(\text{aq}\right)$ have to be given.  The equation has to be balanced and the type of reaction has to be classified.

Concept Introduction:

Refer to part (a).

Answer to Problem 28PE

The reactants that will form ${\text{PbCO}}_{\text{3}}\left(\text{s}\right){\text{+NH}}_{\text{4}}\text{Cl}\left(\text{aq}\right)$ are lead (II) chloride and ammonium carbonate.

The balanced equation is,

  ${\text{PbCl}}_{\text{2}}\left(\text{s}\right)\text{+}{\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{CO}}_{\text{3}}\stackrel{}{\to }{\text{PbCO}}_{\text{3}}\left(\text{s}\right){\text{+2NH}}_{\text{4}}\text{Cl}\left(\text{aq}\right)$

The reaction of lead (II) chloride and ammonium carbonate is a double displacement reaction.

Explanation of Solution

The reactants that will form ${\text{PbCO}}_{\text{3}}\left(\text{s}\right){\text{+NH}}_{\text{4}}\text{Cl}\left(\text{aq}\right)$ are lead (II) chloride and ammonium carbonate.  The chemical equation is,

  ${\text{PbCl}}_{\text{2}}\left(\text{s}\right)\text{+}{\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{CO}}_{\text{3}}\stackrel{}{\to }{\text{PbCO}}_{\text{3}}\left(\text{s}\right){\text{+NH}}_{\text{4}}\text{Cl}\left(\text{aq}\right)$

The above reaction is unbalanced.  The balanced equation is,

  ${\text{PbCl}}_{\text{2}}\left(\text{s}\right)\text{+}{\left({\text{NH}}_{\text{4}}\right)}_{\text{2}}{\text{CO}}_{\text{3}}\stackrel{}{\to }{\text{PbCO}}_{\text{3}}\left(\text{s}\right){\text{+2NH}}_{\text{4}}\text{Cl}\left(\text{aq}\right)$

The reaction of lead (II) chloride and ammonium carbonate to give lead (II) carbonate and ammonium chloride is a double displacement reaction because the cations are interchanged with each other to form new products.