Chapter 18, Problem 18.128P

(a)

Interpretation Introduction

Interpretation:

The ${\text{ FeCl}}_{\text{2}}{\text{, FeCl}}_{\text{3}}{\text{, MgCl}}_{\text{2}}{\text{, KClO}}_{\text{2}}$ salts have to be arranged in decreasing order of $\text{pH}$.

Concept introduction:

Increasing acid strength:

Acids strength is mainly depending on the dissociation of ions, strong acids dissociates completely and weak acid dissociate slightly.

The hydrohalic acids are strong acids ($\text{HCl, HBr, and HI}$) other than ($\text{HF}$).

Oxoacids are strong acid when the number of oxygen excess than the ionizable proton by two or more oxygen atom for example, ${\text{HNO}}_{\text{3}}{\text{, H}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{, and HClO}}_{\text{4}}$.

The hydrogen atom which is not bonded to halogen atom or oxygen atoms are weak acid for example ${\text{HCN, H}}_{\text{2}}\text{S}\text{.}$

The number of protons is equal to number oxygen in Oxoacids are weak acid for example ${\text{ HClO, HNO}}_{\text{2}}{\text{, and H}}_{\text{3}}{\text{PO}}_{\text{4}}$. In general, carboxylic acids are weak acid ($\text{RCOOH}$).

The acid strength is depending on the ${\text{K}}_{\text{a}}$ value, if the  ${\text{K}}_{\text{a}}$ value is larger the stronger the acid. 

Increasing base strength:

The base soluble in water and it contains ${\text{O}}^{\text{2-}}{\text{ or OH}}^{\text{- }}$ is called Strong bases.

In general, Metal oxides and metal hydroxides are more basic compound.

$\begin{array}{l}{\text{M}}_{\text{2}}\text{O or MOH, where M = Group 1A (1) metal (Li, Na, K, Rb, Cs) }\\ {\text{MO or M(OH)}}_{\text{2}}\text{, where M = Group 2A (2) metal (Ca, Sr, Ba) }\end{array}$

Weak bases are ${\text{NH}}_{\text{3}}$ and amines because they contain electron rich nitrogen atom

The aqueous of acidic, basic or neutral is identified by using following method.

The depending on an ion’s ability to react with water,

If the solution is neutral, the anion from strong acid and the cation from strong base.

If the solution is acidic, the anion from strong acid (or highly charged metal cation) and the cation from weak base.

If the solution is basic, the anion from weak acid and the cation from strong base.

Acidic solution:

If the solution is acidic, I would form from cation of weak base and anion of strong acid.

In addition, small, highly charged metal cation and anion of strong acid are acidic solution.

The $\text{pH}$ of the solution is less than seven.

Basic solution:

If the solution is basic, I would form from cation of strong base and anion of weak acid.

Neutral solution:

If the solution is neutral, I would form from cation of strong base and anion of strong acid.

(b)

Interpretation Introduction

Interpretation:

The given ${\text{NH}}_{\text{4}}{\text{Br, NaBrO}}_{\text{2}}{\text{, NaBr, NaClO}}_{\text{2}}$ salts have to be arranged in decreasing order of $\text{pH}$.

Concept introduction:

Increasing acid strength:

Acids strength is mainly depending on the dissociation of ions, strong acids dissociates completely and weak acid dissociate slightly.

The hydrohalic acids are strong acids ($\text{HCl, HBr, and HI}$) other than ($\text{HF}$).

Oxoacids are strong acid when the number of oxygen excess than the ionizable proton by two or more oxygen atom for example, ${\text{HNO}}_{\text{3}}{\text{, H}}_{\text{2}}{\text{SO}}_{\text{4}}{\text{, and HClO}}_{\text{4}}$.

The hydrogen atom which is not bonded to halogen atom or oxygen atoms are weak acid for example ${\text{HCN, H}}_{\text{2}}\text{S}\text{.}$

The number of protons is equal to number oxygen in Oxoacids are weak acid for example ${\text{ HClO, HNO}}_{\text{2}}{\text{, and H}}_{\text{3}}{\text{PO}}_{\text{4}}$. In general, carboxylic acids are weak acid ($\text{RCOOH}$).

The acid strength is depending on the ${\text{K}}_{\text{a}}$ value, if the ${\text{K}}_{\text{a}}$ value is larger the stronger the acid. 

Increasing base strength:

The base soluble in water and it contains ${\text{O}}^{\text{2-}}{\text{ or OH}}^{\text{- }}$ is called Strong bases.

In general, Metal oxides and metal hydroxides are more basic compound.

$\begin{array}{l}{\text{M}}_{\text{2}}\text{O or MOH, where M = Group 1A (1) metal (Li, Na, K, Rb, Cs) }\\ {\text{MO or M(OH)}}_{\text{2}}\text{, where M = Group 2A (2) metal (Ca, Sr, Ba) }\end{array}$

Weak bases are ${\text{NH}}_{\text{3}}$ and amines because they contain electron rich nitrogen atom

The aqueous of acidic, basic or neutral is identified by using following method.

The depending on an ion’s ability to react with water,

If the solution is neutral, the anion from strong acid and the cation from strong base.

If the solution is acidic, the anion from strong acid (or highly charged metal cation) and the cation from weak base.

If the solution is basic, the anion from weak acid and the cation from strong base.

Acidic solution:

If the solution is acidic, I would form from cation of weak base and anion of strong acid.

In addition, small, highly charged metal cation and anion of strong acid are acidic solution.

The $\text{pH}$ of the solution is less than seven.

Basic solution:

If the solution is basic, I would form from cation of strong base and anion of weak acid.

Neutral solution:

If the solution is neutral, I would form from cation of strong base and anion of strong acid.