Chapter 2, Problem 2.49P

Rank the following compounds in order of increasing acidity.

a. ${\text{NH}}_{\text{3}}$, ${\text{H}}_{\text{2}}\text{O}$, $\text{HF}$ e. ${\text{CH}}_3\text{OH}$, ${\text{CH}}_3{\text{NH}}_{\text{2}}$, ${\text{CH}}_3{\text{CH}}_3$

b. $\text{HBr}$, $\text{HCl}$, $\text{HF}$ f. $\text{HCl}$, ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_2\text{S}$

c. ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_3{\text{O}}^{+}$, ${\text{HO}}^{-}$ g. ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$, ${\text{ClCH}}_2{\text{CH}}_{\text{2}}\text{OH}$, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}$

d. ${\text{NH}}_{\text{3}}$, ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_2\text{S}$ h. $\text{HC}\equiv {\text{CCH}}_2{\text{CH}}_{\text{3}}$, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$, ${\text{CH}}_3\text{CH}={\text{CHCH}}_3$

Interpretation Introduction

(a)

Interpretation: The order of increasing acidity for the given compounds is to be stated.

Concept introduction: In a simple molecule, the acidity of a particular proton depends on the atom to which that proton is attached.

In the periodic table, the acidity of a compound increases across a row as the electronegativity increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom. The order of acidity is $\text{C}-\text{H < N}-\text{H < O}-\text{H < F}-\text{H}$.

Answer to Problem 2.49P

The correct order of increasing acidity is ${\text{NH}}_{\text{3}}<{\text{H}}_{\text{2}}\text{O}<\text{HF}$.

Explanation of Solution

The given compounds are ${\text{NH}}_{\text{3}}$, ${\text{H}}_{\text{2}}\text{O}$ and $\text{HF}$.

The given compounds contain $\text{O}-\text{H}$, $\text{N}-\text{H}$ and $\text{F}-\text{H}$ bonds. The acidity of $\text{HA}$ increases across a row as the electronegativity of $\text{A}$ increases on moving from left to right in a periodic table. Hence, the correct order of increasing acidity is ${\text{NH}}_{\text{3}}<{\text{H}}_{\text{2}}\text{O}<\text{HF}$.

Conclusion

The correct order of increasing acidity is ${\text{NH}}_{\text{3}}<{\text{H}}_{\text{2}}\text{O}<\text{HF}$.

Interpretation Introduction

(b)

Interpretation: The order of increasing acidity for the given compounds is to be stated.

Concept introduction: In a simple molecule, the acidity of a particular proton depends on the atom to which that proton is attached.

In the periodic table, the acidity of a compound increases across a row as the electronegativity increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom.

Answer to Problem 2.49P

The correct order of increasing acidity is

Explanation of Solution

The given compounds are $\text{HBr}$, $\text{HCl}$ and $\text{HF}$.

The given compounds contain $\text{Br}-\text{H}$, $\text{Cl}-\text{H}$ and $\text{F}-\text{H}$ bonds. The acidity of a compound increases across a row as the electronegativity increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom. Hence, the correct order of increasing acidity is $\text{HBr}<\text{HCl}<\text{HF}$.

Conclusion

The correct order of increasing acidity is $\text{HBr}<\text{HCl}<\text{HF}$.

Interpretation Introduction

(c)

Interpretation: The order of increasing acidity for the given compounds is to be stated.

Concept introduction: In a simple molecule, the acidity of a particular proton depends on the atom to which that proton is attached.

Answer to Problem 2.49P

The correct order of increasing acidity is ${\text{HO}}^{-}<{\text{H}}_{\text{2}}\text{O}<{\text{H}}_3{\text{O}}^{+}$.

Explanation of Solution

The given compounds are ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_3{\text{O}}^{+}$, and ${\text{HO}}^{-}$.

Hydronium ion (${\text{H}}_3{\text{O}}^{+}$) ionizes to water and a proton, water ionizes to hydroxide and a proton and hydroxide ionizes to form oxide and a proton. The conjugate base formed in case of hydronium is more stable than the conjugate base formed in water and hydroxide. The tendency of hydronium ion to donate its proton is higher than that of water and hydroxide.

Hence, the correct order of increasing acidity is ${\text{HO}}^{-}<{\text{H}}_{\text{2}}\text{O}<{\text{H}}_3{\text{O}}^{+}$.

Conclusion

The correct order of increasing acidity is ${\text{HO}}^{-}<{\text{H}}_{\text{2}}\text{O}<{\text{H}}_3{\text{O}}^{+}$.

Interpretation Introduction

(d)

Interpretation: The order of increasing acidity for the given compounds is to be stated.

Concept introduction: In a simple molecule, the acidity of a particular proton depends on the atom to which that proton is attached.

In the periodic table, the acidity of a compound increases across a row as the electronegativity increases on moving from left to right and down a column as the size of atom increases on moving from top to bottom.

Answer to Problem 2.49P

The correct order of increasing acidity is ${\text{NH}}_{\text{3}}<{\text{H}}_{\text{2}}\text{O}<{\text{H}}_2\text{S}$.

Explanation of Solution

The given compounds are ${\text{NH}}_{\text{3}}$, ${\text{H}}_{\text{2}}\text{O}$, and ${\text{H}}_2\text{S}$.

The given compounds contain $\text{O}-\text{H}$, $\text{N}-\text{H}$ and $\text{S}-\text{H}$ bonds. The acidity of $\text{HA}$ increases across a row as the electronegativity of $\text{A}$ increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom in a periodic table. Hence, the correct order of increasing acidity is ${\text{NH}}_{\text{3}}<{\text{H}}_{\text{2}}\text{O}<{\text{H}}_2\text{S}$.

Conclusion

The correct order of increasing acidity is ${\text{NH}}_{\text{3}}<{\text{H}}_{\text{2}}\text{O}<{\text{H}}_2\text{S}$.

Interpretation Introduction

(e)

Interpretation: The order of increasing acidity for the given compounds is to be stated.

Concept introduction: In a simple molecule, the acidity of a particular proton depends on the atom to which that proton is attached.

In the periodic table, the acidity of a compound increases across a row as the electronegativity increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom. The order of acidity is $\text{C}-\text{H < N}-\text{H < O}-\text{H < F}-\text{H}$.

Answer to Problem 2.49P

The correct order of increasing acidity is ${\text{CH}}_3{\text{CH}}_3<{\text{CH}}_3{\text{NH}}_{\text{2}}<{\text{CH}}_3\text{OH}$.

Explanation of Solution

The given compounds are ${\text{CH}}_3{\text{CH}}_3$, ${\text{CH}}_3{\text{NH}}_{\text{2}}$, and ${\text{CH}}_3\text{OH}$.

The given compounds contain $\text{C}-\text{H}$, $\text{O}-\text{H}$ and $\text{N}-\text{H}$ bonds. The acidity of $\text{HA}$ increases across a row as the electronegativity of $\text{A}$ increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom in a periodic table. Hence, the correct order of increasing acidity is ${\text{CH}}_3{\text{CH}}_3<{\text{CH}}_3{\text{NH}}_{\text{2}}<{\text{CH}}_3\text{OH}$.

Conclusion

The correct order of increasing acidity is ${\text{CH}}_3{\text{CH}}_3<{\text{CH}}_3{\text{NH}}_{\text{2}}<{\text{CH}}_3\text{OH}$.

Interpretation Introduction

(f)

Interpretation: The order of increasing acidity for the given compounds is to be stated.

Concept introduction: In a simple molecule, the acidity of a particular proton depends on the atom to which that proton is attached.

In the periodic table, the acidity of a compound increases across a row as the electronegativity increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom.

Answer to Problem 2.49P

The correct order of increasing acidity is ${\text{H}}_{\text{2}}\text{O}<{\text{H}}_2\text{S}<\text{HCl}$.

Explanation of Solution

The given compounds are ${\text{H}}_{\text{2}}\text{O}$, ${\text{H}}_2\text{S}$ and $\text{HCl}$.

The given compounds contain $\text{O}-\text{H}$, $\text{S}-\text{H}$ and $\text{Cl}-\text{H}$ bonds. The acidity of $\text{HA}$ increases across a row as the electronegativity of $\text{A}$ increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom in a periodic table. Hence, the correct order of increasing acidity is ${\text{H}}_{\text{2}}\text{O}<{\text{H}}_2\text{S}<\text{HCl}$.

Conclusion

The correct order of increasing acidity is ${\text{H}}_{\text{2}}\text{O}<{\text{H}}_2\text{S}<\text{HCl}$.

Interpretation Introduction

(g)

Interpretation: The order of increasing acidity for the given compounds is to be stated.

Concept introduction: In a simple molecule, the acidity of a particular proton depends on the atom to which that proton is attached.

In the periodic table, the acidity of a compound increases across a row as the electronegativity increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom.

Answer to Problem 2.49P

The correct order of increasing acidity is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}<{\text{ClCH}}_2{\text{CH}}_{\text{2}}\text{OH}$.

Explanation of Solution

The given compounds are ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}$, ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}$ and ${\text{ClCH}}_2{\text{CH}}_{\text{2}}\text{OH}$.

The given compounds contain $\text{C}-\text{H}$, and $\text{O}-\text{H}$ bonds. The acidity of $\text{HA}$ increases across a row as the electronegativity of $\text{A}$ increases on moving from left to right and decreases down a column as the size of atom increases on moving from top to bottom in a periodic table. The acidity of the compound increases due to the presence of negative inductive effect of chloro group. Hence, the correct order of increasing acidity is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}<{\text{ClCH}}_2{\text{CH}}_{\text{2}}\text{OH}$.

Conclusion

The correct order of increasing acidity is ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{3}}<{\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}\text{OH}<{\text{ClCH}}_2{\text{CH}}_{\text{2}}\text{OH}$.

Interpretation Introduction

(h)

Interpretation: The order of increasing acidity for the given compounds is to be stated.

Concept introduction: In hydrocarbons, alkanes, alkenes and alkynes, the order of acidity is predicted by their s-character. More is the s-character, more is the acidity.

Answer to Problem 2.49P

The correct order of increasing acidity is,

Explanation of Solution

The given compounds are,

Figure 1

For alkanes, alkenes and alkynes, the order of s-character is,

$\text{Alkyne}>\text{Alkene}>\text{Alkane}$

More is the s-character of a compound, more is the acidity. Hence, the correct order of increasing acidity is shown below.

Figure 2

Conclusion

The correct order of increasing acidity is shown in Figure 2.