Chapter 14, Problem 14QRT

(a)

Interpretation Introduction

Interpretation:

Conjugate partner for ${\text{CN}}^{-}$ has to be given along with the name.

Concept Introduction:

Brønsted-Lowry acid is the one which can donate ${\text{H}}^{\text{+}}$ ion to other substances.  It can also be said as proton donors.  Brønsted-Lowry base is the one which can accept ${\text{H}}^{\text{+}}$ ion from other substances.  It can also be said as proton acceptors.  In order to be a Brønsted-Lowry base, an unshared pair of electrons must be present on molecule or the ion.

Difference between conjugate acid-base pair is ${\text{H}}^{\text{+}}$ ion.  For a Brønsted-Lowry acid, the conjugate base has fewer ${\text{H}}^{\text{+}}$ and for Brønsted-Lowry base, the conjugate acid has more ${\text{H}}^{\text{+}}$.

Explanation of Solution

Given formula is ${\text{CN}}^{-}$.  This is a Brønsted-Lowry base, as this does not have ${\text{H}}^{\text{+}}$ ions.  When this is added to water, a proton is transferred from water resulting in formation of ${\text{OH}}^{-}(aq)$ along with conjugate acid.  This can be represented in chemical equation as,

    ${\text{CN}}^{-}+{\text{H}}_{\text{2}}\text{O(l)}\rightleftharpoons \text{HCN}(aq)+{\text{OH}}^{-}(aq)$

Conjugate partner of ${\text{CN}}^{-}$ is $\text{HCN}$.  The formed conjugate partner is named as hydrogen cyanide.

(b)

Interpretation Introduction

Interpretation:

Conjugate partner for ${\text{SO}}_{\text{4}}{}^{2-}$ has to be given along with the name.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given formula is ${\text{SO}}_{\text{4}}{}^{2-}$.  This is a Brønsted-Lowry base, as this does not have ${\text{H}}^{\text{+}}$ ions.  When this is added to water, a proton is transferred from water resulting in formation of ${\text{OH}}^{-}(aq)$ along with conjugate acid.  This can be represented in chemical equation as,

    ${\text{SO}}_{\text{4}}{}^{2-}+{\text{H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{HSO}}_{\text{4}}{}^{-}(aq)+{\text{OH}}^{-}(aq)$

Conjugate partner of ${\text{SO}}_{\text{4}}{}^{2-}$ is ${\text{HSO}}_{\text{4}}{}^{-}$.  The formed conjugate partner is named as hydrogen sulfate.

(c)

Interpretation Introduction

Interpretation:

Conjugate partner for ${\text{HS}}^{-}$ has to be given along with the name.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given formula is ${\text{HS}}^{-}$.  This can act as both Brønsted-Lowry acid and Brønsted-Lowry base.

Conjugate partner when ${\text{HS}}^{-}$ acts as Brønsted-Lowry acid:

When this is added to water, a proton is transferred from acid to the water resulting in formation of ${\text{H}}_{\text{3}}{\text{O}}^{+}(aq)$ along with conjugate base.  This can be represented in chemical equation as,

    ${\text{HS}}^{-}+{\text{H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{S}}^{2-}(aq)+{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}(aq)$

Conjugate partner of ${\text{HS}}^{-}$ is ${\text{S}}^{2-}$.  The formed conjugate partner is named as sulfide ion.

Conjugate partner when ${\text{HS}}^{-}$ acts as Brønsted-Lowry base:

When this is added to water, a proton is transferred from water to the base resulting in formation of ${\text{OH}}^{-}(aq)$ along with conjugate acid.  This can be represented in chemical equation as,

    ${\text{HS}}^{-}+{\text{H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{H}}_{\text{2}}\text{S}(aq)+{\text{OH}}^{-}(aq)$

Conjugate partner of ${\text{HS}}^{-}$ is ${\text{H}}_{\text{2}}\text{S}$.  The formed conjugate partner is named as hydrosulfuric acid.

(d)

Interpretation Introduction

Interpretation:

Conjugate partner for ${\text{S}}^{2-}$ has to be given along with the name.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given formula is ${\text{S}}^{2-}$.  This is a Brønsted-Lowry base, as this does not have ${\text{H}}^{\text{+}}$ ions.  When this is added to water, a proton is transferred from water resulting in formation of ${\text{OH}}^{-}(aq)$ along with conjugate acid.  This can be represented in chemical equation as,

    ${\text{S}}^{2-}+{\text{H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{HS}}^{-}(aq)+{\text{OH}}^{-}(aq)$

Conjugate partner of ${\text{S}}^{2-}$ is ${\text{HS}}^{-}$.  The formed conjugate partner is named as hydrogen sulfide anion.

(e)

Interpretation Introduction

Interpretation:

Conjugate partner for ${\text{HSO}}_{\text{3}}{}^{-}$ has to be given along with the name.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given formula is ${\text{HSO}}_{\text{3}}{}^{-}$.  This can act as both Brønsted-Lowry acid and Brønsted-Lowry base.

Conjugate partner when ${\text{HSO}}_{\text{3}}{}^{-}$ acts as Brønsted-Lowry acid:

When this is added to water, a proton is transferred from acid to the water resulting in formation of ${\text{H}}_{\text{3}}{\text{O}}^{+}(aq)$ along with conjugate base.  This can be represented in chemical equation as,

    ${\text{HSO}}_{\text{3}}{}^{-}+{\text{H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{SO}}_{\text{3}}{}^{2-}(aq)+{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}(aq)$

Conjugate partner of ${\text{HSO}}_{\text{3}}{}^{-}$ is ${\text{SO}}_{\text{3}}{}^{2-}$.  The formed conjugate partner is named as sulfite ion.

Conjugate partner when ${\text{HSO}}_{\text{3}}{}^{-}$ acts as Brønsted-Lowry base:

When this is added to water, a proton is transferred from water to the base resulting in formation of ${\text{OH}}^{-}(aq)$ along with conjugate acid.  This can be represented in chemical equation as,

    ${\text{HSO}}_{\text{3}}{}^{-}+{\text{H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{H}}_{\text{2}}{\text{SO}}_{\text{3}}(aq)+{\text{OH}}^{-}(aq)$

Conjugate partner of ${\text{HSO}}_{\text{3}}{}^{-}$ is ${\text{H}}_{\text{2}}{\text{SO}}_{\text{3}}$.  The formed conjugate partner is named as sulfurous acid.

(f)

Interpretation Introduction

Interpretation:

Conjugate partner for $\text{HCOOH}$ has to be given along with the name.

Concept Introduction:

Refer part (a).

Explanation of Solution

Given formula is $\text{HCOOH}$.  This is a Brønsted-Lowry acid, as this has one more ${\text{H}}^{\text{+}}$ ion.  When this is added to water, a proton is transferred from acid to the water resulting in formation of ${\text{H}}_{\text{3}}{\text{O}}^{+}(aq)$ along with conjugate base.  This can be represented in chemical equation as,

    $\text{HCOOH}+{\text{H}}_{\text{2}}\text{O(l)}\rightleftharpoons {\text{HCOO}}^{-}(aq)+{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}(aq)$

Conjugate partner of $\text{HCOOH}$ is ${\text{HCOO}}^{-}$.  The formed conjugate partner is named as formate ion.