Chapter 19.1, Problem 19.2CYU

(a)

Interpretation Introduction

Interpretation:

The following redox equation in basic solution has to be given.

$\text{Al(s) + S(s) }\to {\text{Al(OH)}}_{\text{3}}{\text{(s) + HS}}^{-}\text{(aq)}$

Concept introduction:

Steps for balancing half –reactions in BASIC solution:

1. 1. Recognize the reaction as an oxidation and reduction reaction.
2. 2. Separate two half reactions.
3. 3.  Balance half reactions by mass

   Balance all atoms except H and O in half reaction.

   Addition of ${\text{OH}}^{\text{-}}$ or ${\text{OH}}^{\text{-}}{\text{ and H}}_{\text{2}}\text{O}$ is required for mass balance in both half reactions.

4. 4. Balance the charge by adding electrons to side with more total positive charge.
5. 5. Multiply the half reactions by appropriate factors.
6. 6. Add two half reactions and cancel the common atoms.
7. 7. Simplify by eliminating reactants and products that appears on both sides.

(b)

Interpretation Introduction

Interpretation:

It has to be identified the oxidizing and reducing agents in the following reaction.

$\text{Al(s) + S(s) }\to {\text{Al(OH)}}_{\text{3}}{\text{(s) + HS}}^{-}\text{(aq)}$

Concept introduction:

Oxidation reaction:

The loss of electrons or the gain of oxygen atoms.And also their oxidation number get increases.

$\text{Ag }\to {\text{ Ag}}^{\text{+}}{\text{+ e}}^{\text{-}}$

In the above reaction , Ag atom lose one electron and change their oxidation state 0 to 1.

Reduction reaction:

Gaining electrons or adding hydrogen atoms. And also decrease their oxidation number.

${\text{Fe}}^{\text{2+}}{\text{+2e}}^{\text{-}}\to \text{ Fe}$

In the above reaction ${\text{Fe}}^{\text{2+}}$ ion gaining 2 electrons and reduce their oxidation number +2 to 0.

Oxidizing agent: A reagent that increases the oxidation number of an element.

Reducing agent: A reagent that lowers the oxidation number of a given element.