Chapter 8, Problem 6P

8-18 Which of these acids are monoprotic, which are diprotic, and which are triprotic? Which are amphiprotic?

(a) H₂PO₄-

(b) HBO₃²-

(c) HCIO₄

(d) C₂H₅OH

(e) HSO₃-

(f) HS-

(g) H₂CO₃

Interpretation Introduction

(a)

Interpretation:

The given chemical substance is monoprotic, diprotic or triprotic to be identified.

Concept Introduction:

A chemical substance which releases single proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as monoprotic acid.

A chemical substance which releases two proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as diprotic acid.

A chemical substance which releases three proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as triprotic acid.

A chemical substance which can release or accepts a proton or hydronium ion in aqueous solution to behave as acid or base is termed as amphiprotic.

Answer to Problem 6P

H₂ PO₄ - is amphiprotic.

Explanation of Solution

H₂ PO₄ - is amphiprotic as it can release or accepts a proton as follows:

H₂ PO₄ - releases proton in aqueous solution and releases hydronium ion as follows:

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{}^{\text{-}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{ HPO}}_{\text{4}}{}^{\text{-2}}{\text{+ H}}_{\text{3}}{\text{O}}^{\text{+}}$

H₂ PO₄ -gains proton in aqueous solution and releases hydroxide ion as follows:

${\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{}^{\text{-}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{H}}_{\text{3}}{\text{PO}}_{\text{4}}{\text{+ OH}}^{\text{-}}$.

Interpretation Introduction

(b)

Interpretation:

The given chemical substance is monoprotic, diprotic or triprotic to be identified.

Concept Introduction:

A chemical substance which releases single proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as monoprotic acid.

A chemical substance which releases two proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as diprotic acid.

A chemical substance which releases three proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as triprotic acid.

A chemical substance which can release or accepts a proton or hydronium ion in aqueous solution to behave as acid or base is termed as amphiprotic.

Answer to Problem 6P

HBO₃ -2 is amphiprotic.

Explanation of Solution

HBO₃ -2 is amphiprotic as it can release or accepts a proton as follows:

HBO₃ -2 releases proton in aqueous solution and releases hydronium ion as follows:

${\text{HBO}}_{\text{3}}{}^{\text{-2}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{BO}}_{\text{3}}{}^{\text{-3}}{\text{+ H}}_{\text{3}}{\text{O}}^{\text{+}}$

HBO₃ -² gains proton in aqueous solution and releases hydroxide ion as follows:

${\text{HBO}}_{\text{3}}{}^{\text{-2}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{H}}_{\text{2}}{\text{BO}}_{\text{3}}{}^{\text{-}}{\text{+ OH}}^{\text{-}}$.

Interpretation Introduction

(c)

Interpretation:

The given chemical substance is monoprotic, diprotic or triprotic to be identified.

Concept Introduction:

A chemical substance which releases single proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as monoprotic acid.

A chemical substance which releases two proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as diprotic acid.

A chemical substance which releases three proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as triprotic acid.

A chemical substance which can release or accepts a proton or hydronium ion in aqueous solution to behave as acid or base is termed as amphiprotic.

Answer to Problem 6P

HClO₄ is monoprotic acid.

Explanation of Solution

HClO₄ is monoprotic acid as it can release only one proton in aqueous solution and releases hydronium ion as follows:

${\text{HClO}}_{\text{4}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{ClO}}_{\text{4}}{}^{\text{-}}{\text{+ H}}_{\text{3}}{\text{O}}^{\text{+}}$.

Interpretation Introduction

(d)

Interpretation:

The given chemical substance is monoprotic, diprotic or triprotic to be identified.

Concept Introduction:

A chemical substance which releases single proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as monoprotic acid.

A chemical substance which releases two proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as diprotic acid.

A chemical substance which releases three proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as triprotic acid.

A chemical substance which can release or accepts a proton or hydronium ion in aqueous solution to behave as acid or base is termed as amphiprotic.

Answer to Problem 6P

C₂ H₅ OH is monoprotic acid.

Explanation of Solution

C₂ H₅ OH is monoprotic acid as it can release only one proton in aqueous solution and releases hydronium ion as follows:

${\text{C}}_{\text{2}}{\text{H}}_{\text{5}}{\text{OH + H}}_{\text{2}}\text{O }\to {\text{C}}_{\text{2}}{\text{H}}_{\text{5}}{\text{O}}^{\text{-}}{\text{+ H}}_{\text{3}}{\text{O}}^{\text{+}}$.

Interpretation Introduction

(e)

Interpretation:

The given chemical substance is monoprotic, diprotic or triprotic to be identified.

Concept Introduction:

A chemical substance which releases single proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as monoprotic acid.

A chemical substance which releases two proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as diprotic acid.

A chemical substance which releases three proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as triprotic acid.

A chemical substance which can release or accepts a proton or hydronium ion in aqueous solution to behave as acid or base is termed as amphiprotic.

Answer to Problem 6P

HSO₃ - is amphiprotic.

Explanation of Solution

HSO₃ - is amphiprotic as it can release or accepts a proton as follows:

HSO₃ -2 releases proton in aqueous solution and releases hydronium ion as follows:

${\text{HSO}}_{\text{3}}{}^{\text{-2}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{SO}}_{\text{3}}{}^{\text{-3}}{\text{+ H}}_{\text{3}}{\text{O}}^{\text{+}}$

HSO₃ -² gains proton in aqueous solution and releases hydroxide ion as follows:

${\text{HSO}}_{\text{3}}{}^{\text{-2}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{ H}}_{\text{2}}{\text{SO}}_{\text{3}}{}^{\text{-}}{\text{+ OH}}^{\text{-}}$.

Interpretation Introduction

(f)

Interpretation:

The given chemical substance is monoprotic, diprotic or triprotic to be identified.

Concept Introduction:

A chemical substance which releases single proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as monoprotic acid.

A chemical substance which releases two proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as diprotic acid.

A chemical substance which releases three proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as triprotic acid.

A chemical substance which can release or accepts a proton or hydronium ion in aqueous solution to behave as acid or base is termed as amphiprotic.

Answer to Problem 6P

HS- is amphiprotic.

Explanation of Solution

HS- is amphiprotic as it can release or accepts a proton as follows:

HS- releases proton in aqueous solution and releases hydronium ion as follows:

${\text{HS}}^{\text{-}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{S}}^{\text{-2}}{\text{+ H}}_{\text{3}}{\text{O}}^{\text{+}}$

HS-gains proton in aqueous solution and releases hydroxide ion as follows:

${\text{HS}}^{\text{-}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{ H}}_{\text{2}}{\text{S + OH}}^{\text{-}}$.

Interpretation Introduction

(g)

Interpretation:

The given chemical substance is monoprotic, diprotic or triprotic to be identified.

Concept Introduction:

A chemical substance which releases single proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as monoprotic acid.

A chemical substance which releases two proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as diprotic acid.

A chemical substance which releases three proton or hydronium ion per molecule on dissociation in the aqueous solution is termed as triprotic acid.

A chemical substance which can release or accepts a proton or hydronium ion in aqueous solution to behave as acid or base is termed as amphiprotic.

Answer to Problem 6P

H₂ CO₃ is diprotic acid.

Explanation of Solution

H₂ CO₃ is diprotic acid as it can release twoproton in aqueous solution and releases hydronium ion as follows:

${\text{H}}_{\text{2}}{\text{CO}}_{\text{3}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{HCO}}_{\text{3}}{}^{\text{-}}{\text{+ H}}_{\text{3}}{\text{O}}^{\text{+}}$

${\text{HCO}}_{\text{3}}{}^{\text{-}}{\text{+ H}}_{\text{2}}\text{O }\to {\text{CO}}_{\text{3}}{}^{\text{-2}}{\text{+ H}}_{\text{3}}{\text{O}}^{\text{+}}$.