Chapter 15.1, Problem 20PP

(a)

Interpretation Introduction

Interpretation: For the following reaction, identify the substances that is oxidized, the substance that is reduced, the oxidizing agent, and the reducing agent.

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

Concept Introduction: In an oxidation reaction the oxidation number of the element increase or becomes more positive. In a reduction reaction the oxidation number of the element decrease or becomes more negative.

The rules for assigning oxidation number to elements are:

• For an element in its free state it is assigned an oxidation number of zero.
• Monatomic ions have oxidation number that is equal to charge of the monatomic ion.
• Alkali metals have +1 oxidation number, alkaline earth metals have +2 oxidation number and halogens are assigned -1 oxidation number.
• In most compounds H is assigned a +1 oxidation number and O is assigned a -2 oxidation number.
• For a neutral compound the summation of oxidation numbers of all elements in the compound is zero.

(b)

Interpretation Introduction

Interpretation: For the following reaction, identify the substances that is oxidized, the substance that is reduced, the oxidizing agent, and the reducing agent.

  $\text{Zn}\left(\text{s}\right)\text{ + 2HCl}\left(\text{aq}\right)\to {\text{ZnCl}}_{\text{2}}\left(\text{aq}\right){\text{ + H}}_{\text{2}}\left(\text{g}\right)$

Concept Introduction: In an oxidation reaction the oxidation number of the element increase or becomes more positive. In a reduction reaction the oxidation number of the element decrease or becomes more negative.

The rules for assigning oxidation number to elements are:

• For an element in its free state it is assigned an oxidation number of zero.
• Monatomic ions have oxidation number that is equal to charge of the monatomic ion.
• Alkali metals have +1 oxidation number, alkaline earth metals have +2 oxidation number and halogens are assigned -1 oxidation number.
• In most compounds H is assigned a +1 oxidation number and O is assigned a -2 oxidation number.
• For a neutral compound the summation of oxidation numbers of all elements in the compound is zero.

(c)

Interpretation Introduction

Interpretation: For the following reaction, identify the substances that is oxidized, the substance that is reduced, the oxidizing agent, and the reducing agent.

  $\text{2Na}\left(\text{s}\right){\text{ + 2H}}_{\text{2}}\text{O}\left(\text{l}\right)\to {\text{2Na}}^{\text{+}}\left(\text{aq}\right){\text{ + 2OH}}^{\text{-}}\left(\text{aq}\right){\text{ + H}}_{\text{2}}\left(\text{g}\right)$

Concept Introduction: In an oxidation reaction the oxidation number of the element increase or becomes more positive. In a reduction reaction the oxidation number of the element decrease or becomes more negative.

The rules for assigning oxidation number to elements are:

• For an element in its free state it is assigned an oxidation number of zero.
• Monatomic ions have oxidation number that is equal to charge of the monatomic ion.
• Alkali metals have +1 oxidation number, alkaline earth metals have +2 oxidation number and halogens are assigned -1 oxidation number.
• In most compounds H is assigned a +1 oxidation number and O is assigned a -2 oxidation number.
• For a neutral compound the summation of oxidation numbers of all elements in the compound is zero.

(d)

Interpretation Introduction

Interpretation: For the following reaction, identify the substances that is oxidized, the substance that is reduced, the oxidizing agent, and the reducing agent.

  ${\text{14H}}^{\text{+}}\left(\text{aq}\right){\text{ + 6Fe}}^{\text{2+}}\left(\text{aq}\right){\text{ +Cr}}_{\text{2}}{\text{O}}_{\text{7}}{}^{\text{2-}}\left(\text{aq}\right)\to {\text{6Fe}}^{\text{3+}}\left(\text{aq}\right){\text{ + 2Cr}}^{\text{3+}}\left(\text{aq}\right){\text{ + 7H}}_{\text{2}}\text{O}\left(\text{l}\right)$

Concept Introduction: In an oxidation reaction the oxidation number of the element increase or becomes more positive. In a reduction reaction the oxidation number of the element decrease or becomes more negative.

The rules for assigning oxidation number to elements are:

• For an element in its free state it is assigned an oxidation number of zero.
• Monatomic ions have oxidation number that is equal to charge of the monatomic ion.
• Alkali metals have +1 oxidation number, alkaline earth metals have +2 oxidation number and halogens are assigned -1 oxidation number.
• In most compounds H is assigned a +1 oxidation number and O is assigned a -2 oxidation number.
• For a neutral compound the summation of oxidation numbers of all elements in the compound is zero.