# 14.1 Brønsted-lowry acids and bases  (Page 4/14)

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${\text{2H}}_{2}\text{O(}l\right)\phantom{\rule{0.2em}{0ex}}⇌\phantom{\rule{0.2em}{0ex}}{\text{H}}_{3}{\text{O}}^{+}\left(aq\right)+{\text{OH}}^{\text{−}}\left(aq\right)$

The ion product of water, K w is the equilibrium constant for the autoionization reaction:

${K}_{\text{w}}=\left[{\text{H}}_{3}{\text{O}}^{\text{+}}\right]\left[{\text{OH}}^{\text{−}}\right]=1.0\phantom{\rule{0.2em}{0ex}}×\phantom{\rule{0.2em}{0ex}}1{0}^{-14}\phantom{\rule{0.2em}{0ex}}\text{at}\phantom{\rule{0.2em}{0ex}}25\phantom{\rule{0.2em}{0ex}}\text{°C}$

## Key equations

• K w = [H 3 O + ][OH ] = 1.0 $×$ 10 −14 (at 25 °C)

## Chemistry end of chapter exercises

Write equations that show NH 3 as both a conjugate acid and a conjugate base.

One example for NH 3 as a conjugate acid: ${\text{NH}}_{2}{}^{\text{−}}+{\text{H}}^{\text{+}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{NH}}_{3};$ as a conjugate base: ${\text{NH}}_{4}{}^{\text{+}}\left(aq\right)+{\text{OH}}^{\text{−}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{NH}}_{3}\left(aq\right)+{\text{H}}_{2}\text{O}\left(l\right)$

Write equations that show ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}$ acting both as an acid and as a base.

Show by suitable net ionic equations that each of the following species can act as a Brønsted-Lowry acid:

(a) ${\text{H}}_{3}{\text{O}}^{\text{+}}$

(b) HCl

(c) NH 3

(d) CH 3 CO 2 H

(e) ${\text{NH}}_{4}{}^{\text{+}}$

(f) ${\text{HSO}}_{4}{}^{\text{−}}$

(a) ${\text{H}}_{3}{\text{O}}^{\text{+}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}^{\text{+}}\left(aq\right)+{\text{H}}_{2}\text{O}\left(l\right);$ (b) $\text{HCl}\left(l\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}^{\text{+}}\left(aq\right)+{\text{Cl}}^{\text{−}}\left(aq\right);$ (c) ${\text{NH}}_{3}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}^{\text{+}}\left(aq\right)+{\text{NH}}_{2}{}^{\text{−}}\left(aq\right);$ (d) ${\text{CH}}_{3}{\text{CO}}_{2}\text{H}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}^{\text{+}}\left(aq\right)+{\text{CH}}_{3}{\text{CO}}_{2}{}^{\text{−}}\left(aq\right);$ (e) ${\text{NH}}_{4}{}^{\text{+}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}^{\text{+}}\left(aq\right)+{\text{NH}}_{3}\left(aq\right);$ (f) ${\text{HSO}}_{4}{}^{\text{−}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}^{+}\left(aq\right)+{\text{SO}}_{4}{}^{\text{2−}}\left(aq\right)$

Show by suitable net ionic equations that each of the following species can act as a Brønsted-Lowry acid:

(a) HNO 3

(b) ${\text{PH}}_{4}{}^{\text{+}}$

(c) H 2 S

(d) CH 3 CH 2 COOH

(e) ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}$

(f) HS

Show by suitable net ionic equations that each of the following species can act as a Brønsted-Lowry base:

(a) H 2 O

(b) OH

(c) NH 3

(d) CN

(e) S 2−

(f) ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}$

(a) ${\text{H}}_{2}\text{O}\left(l\right)+{\text{H}}^{\text{+}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}_{3}{\text{O}}^{\text{+}}\left(aq\right);$ (b) ${\text{OH}}^{\text{−}}\left(aq\right)+{\text{H}}^{\text{+}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}_{2}\text{O}\left(l\right);$ (c) ${\text{NH}}_{3}\left(aq\right)+{\text{H}}^{\text{+}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{NH}}_{4}{}^{\text{+}}\left(aq\right);$ (d) ${\text{CN}}^{\text{−}}\left(aq\right)+{\text{H}}^{\text{+}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{HCN}\left(aq\right);$ (e) ${\text{S}}^{2-}\left(aq\right)+{\text{H}}^{\text{+}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{HS}}^{\text{−}}\left(aq\right);$ (f) ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}\left(aq\right)+{\text{H}}^{\text{+}}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}_{3}{\text{PO}}_{4}\left(aq\right)$

Show by suitable net ionic equations that each of the following species can act as a Brønsted-Lowry base:

(a) HS

(b) ${\text{PO}}_{4}{}^{\text{3−}}$

(c) ${\text{NH}}_{2}{}^{\text{−}}$

(d) C 2 H 5 OH

(e) O 2−

(f) ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}$

What is the conjugate acid of each of the following? What is the conjugate base of each?

(a) OH

(b) H 2 O

(c) ${\text{HCO}}_{3}{}^{\text{−}}$

(d) NH 3

(e) ${\text{HSO}}_{4}{}^{\text{−}}$

(f) H 2 O 2

(g) HS

(h) ${\text{H}}_{5}{\text{N}}_{2}{}^{\text{+}}$

(a) H 2 O, O 2− ; (b) H 3 O + , OH ; (c) H 2 CO 3 , ${\text{CO}}_{3}{}^{\text{2−}};$ (d) ${\text{NH}}_{4}{}^{\text{+}},$ ${\text{NH}}_{2}{}^{\text{−}};$ (e) H 2 SO 4 , ${\text{SO}}_{4}{}^{\text{2−}};$ (f) ${\text{H}}_{3}{\text{O}}_{2}{}^{\text{+}},$ ${\text{HO}}_{2}{}^{\text{−}};$ (g) H 2 S; S 2− ; (h) ${\text{H}}_{6}{\text{N}}_{2}{}^{2+},$ H 4 N 2

What is the conjugate acid of each of the following? What is the conjugate base of each?

(a) H 2 S

(b) ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}$

(c) PH 3

(d) HS

(e) ${\text{HSO}}_{3}{}^{\text{−}}$

(f) ${\text{H}}_{3}{\text{O}}_{2}{}^{\text{+}}$

(g) H 4 N 2

(h) CH 3 OH

Identify and label the Brønsted-Lowry acid, its conjugate base, the Brønsted-Lowry base, and its conjugate acid in each of the following equations:

(a) ${\text{HNO}}_{3}+{\text{H}}_{2}\text{O}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}_{3}{\text{O}}^{\text{+}}+{\text{NO}}_{3}{}^{\text{−}}$

(b) ${\text{CN}}^{\text{−}}+{\text{H}}_{2}\text{O}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{HCN}+{\text{OH}}^{\text{−}}$

(c) ${\text{H}}_{2}{\text{SO}}_{4}+{\text{Cl}}^{\text{−}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{HCl}+{\text{HSO}}_{4}{}^{\text{−}}$

(d) ${\text{HSO}}_{4}{}^{\text{−}}+{\text{OH}}^{\text{−}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{SO}}_{4}{}^{\text{2−}}+{\text{H}}_{2}\text{O}$

(e) ${\text{O}}^{2-}+{\text{H}}_{2}\text{O}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}2{\mathrm{OH}}^{\text{−}}$

(f) ${\left[\text{Cu}{\left({\text{H}}_{2}\text{O}\right)}_{3}\left(\text{OH}\right)\right]}^{\text{+}}+{\left[\text{Al}{\left({\text{H}}_{2}\text{O}\right)}_{6}\right]}^{3+}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\left[\text{Cu}{\left({\text{H}}_{2}\text{O}\right)}_{4}\right]}^{2+}+{\left[\text{Al}{\left({\text{H}}_{2}\text{O}\right)}_{5}\left(\text{OH}\right)\right]}^{2+}$

(g) ${\text{H}}_{2}\text{S}+{\text{NH}}_{2}{}^{\text{−}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{HS}}^{\text{−}}+{\text{NH}}_{3}$

The labels are Brønsted-Lowry acid = BA; its conjugate base = CB; Brønsted-Lowry base = BB; its conjugate acid = CA. (a) HNO 3 (BA), H 2 O(BB), H 3 O + (CA), ${\text{NO}}_{3}{}^{\text{−}}\left(\text{CB}\right);$ (b) CN (BB), H 2 O(BA), HCN(CA), OH (CB); (c) H 2 SO 4 (BA), Cl (BB), HCl(CA), ${\text{HSO}}_{4}{}^{\text{−}}\left(\text{CB}\right);$ (d) ${\text{HSO}}_{4}{}^{\text{−}}\left(\text{BA}\right),$ OH (BB), ${\text{SO}}_{4}{}^{\text{2−}}$ (CB), H 2 O(CA); (e) O 2− (BB), H 2 O(BA) OH (CB and CA); (f) [Cu(H 2 O) 3 (OH)] + (BB), [Al(H 2 O) 6 ] 3+ (BA), [Cu(H 2 O) 4 ] 2+ (CA), [Al(H 2 O) 5 (OH)] 2+ (CB); (g) H 2 S(BA), ${\text{NH}}_{2}{}^{\text{−}}\left(\text{BB}\right),$ HS (CB), NH 3 (CA)

Identify and label the Brønsted-Lowry acid, its conjugate base, the Brønsted-Lowry base, and its conjugate acid in each of the following equations:

(a) ${\text{NO}}_{2}{}^{\text{−}}+{\text{H}}_{2}\text{O}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{HNO}}_{2}+{\text{OH}}^{\text{−}}$

(b) $\text{HBr}+{\text{H}}_{2}\text{O}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}_{3}{\text{O}}^{\text{+}}+{\text{Br}}^{\text{−}}$

(c) ${\text{HS}}^{\text{−}}+{\text{H}}_{2}\text{O}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}_{2}\text{S}+{\text{OH}}^{\text{−}}$

(d) ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}+{\text{OH}}^{\text{−}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{HPO}}_{4}{}^{\text{2−}}+{\text{H}}_{2}\text{O}$

(e) ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}+\text{HCl}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}_{3}{\text{PO}}_{4}+{\text{Cl}}^{\text{−}}$

(f) ${\left[\text{Fe}{\left({\text{H}}_{2}\text{O}\right)}_{5}\left(\text{OH}\right)\right]}^{2+}+{\left[\text{Al}{\left({\text{H}}_{2}\text{O}\right)}_{6}\right]}^{3+}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{[Fe}{\left({\text{H}}_{2}\text{O}\right)}_{6}\right]}^{3+}+{\left[\text{Al}{\left({\text{H}}_{2}\text{O}\right)}_{5}\left(\text{OH}\right)\right]}^{2+}$

(g) ${\text{CH}}_{3}\text{OH}+{\text{H}}^{\text{−}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{CH}}_{3}{\text{O}}^{\text{−}}+{\text{H}}_{2}$

What are amphiprotic species? Illustrate with suitable equations.

Amphiprotic species may either gain or lose a proton in a chemical reaction, thus acting as a base or an acid. An example is H 2 O. As an acid:
${\text{H}}_{2}\text{O}\left(aq\right)+{\text{NH}}_{3}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⇌\phantom{\rule{0.2em}{0ex}}{\text{NH}}_{4}{}^{\text{+}}\left(aq\right)+{\text{OH}}^{\text{−}}\left(aq\right).$ As a base: ${\text{H}}_{2}\text{O}\left(aq\right)+\text{HCl}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⇌\phantom{\rule{0.2em}{0ex}}{\text{H}}_{3}{\text{O}}^{\text{+}}\left(aq\right)+{\text{Cl}}^{\text{−}}\left(aq\right)$

State which of the following species are amphiprotic and write chemical equations illustrating the amphiprotic character of these species:

(a) H 2 O

(b) ${\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}$

(c) S 2−

(d) ${\text{CO}}_{3}{}^{\text{2−}}$

(e) ${\text{HSO}}_{4}{}^{\text{−}}$

State which of the following species are amphiprotic and write chemical equations illustrating the amphiprotic character of these species.

(a) NH 3

(b) ${\text{HPO}}_{4}{}^{\text{−}}$

(c) Br

(d) ${\text{NH}}_{4}{}^{\text{+}}$

(e) ${\text{ASO}}_{4}{}^{\text{3−}}$

amphiprotic: (a) ${\text{NH}}_{3}+{\text{H}}_{3}{\text{O}}^{\text{+}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{NH}}_{4}\text{OH}+{\text{H}}_{2}\text{O},$ ${\text{NH}}_{3}+{\text{OCH}}_{3}{}^{\text{−}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{NH}}_{2}{}^{\text{−}}+{\text{CH}}_{3}\text{OH};$ (b) ${\text{HPO}}_{4}{}^{\text{2−}}+{\text{OH}}^{\text{−}}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{PO}}_{4}{}^{\text{3−}}+{\text{H}}_{2}\text{O},$ ${\text{HPO}}_{4}{}^{\text{2−}}+{\text{HClO}}_{4}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{H}}_{2}{\text{PO}}_{4}{}^{\text{−}}+{\text{ClO}}_{4}{}^{\text{−}};$ not amphiprotic: (c) Br ; (d) ${\text{NH}}_{4}{}^{\text{+}};$ (e) ${\text{AsO}}_{4}{}^{\text{3−}}$

Is the self ionization of water endothermic or exothermic? The ionization constant for water ( K w ) is 2.9 $×$ 10 −14 at 40 °C and 9.3 $×$ 10 −14 at 60 °C.

#### Questions & Answers

definition of isomerism
who is the father of chemistry
what is hybridization and bonding
please who is the father of chemistry
Naomi
Antoine Lavoisier
Abdelkarim
Abdelkarim
Also, god has created everything
Abdelkarim
(Allah, the creator)
Abdelkarim
how to determine the empirical formula
what is neutralisation reaction
It is a reaction where an acid (aq) reacts with an alkali (aq) to form salt AND water.
Abdelkarim
What is the ratio of the average kinetic energy of a SO 2 molecule to that of an O 2 molecule in a mixture of two gases? What is the ratio of the root mean square speeds, u rms , of the two gases?
what is methyl orange
its an indicator
Abigail
It is an organic molecule that reacts with acid/base medium and shows change in colour (due to formed products). It can be used to test for alcohols which are prohibited to drink in Islam as it is bad for brain and liver and immunity.
Abdelkarim
it is an indicator used to determine the end point in an acid-base titration
xMah_Bx
Abdelkarim
covalent bond explanation
God has lictured these rules that the electrons move with them and the space time curve. So we prwy to God in Islam or we suffer. Please learn about Islam and science and mention God and thank him.
Abdelkarim
yes, it is very true. God is the one who inspires science. Then we, as his children, have the privilege to learn about what he has created. I'm still a novis at chemistry. I still have a lot to learn.
Eric
Beautiful, however, what I learned from the Quran is that god has created human and has a mission like managing the ecology, building, learning, mentioning god (saying glory to Almighty for instance few times and periodic). And the moat important prayer lile prophet Muhammed the last meassenger.
Abdelkarim
Also God forgives all sins except assossiating any one with him like sons and daughters or stone sculpture. Beautifully, if some one stops from saying this God can switch their sins to virtueness. And God all merciful doesnt get bored forgiving people who ask for forgiveness.
Abdelkarim
Also, there is a versw in the Quran that sates: { corruption has appeared in the land and the sea he will taste them from what their hands have gained} this reminds me of covid from stupid politicians who will be throne to hell.
Abdelkarim
nature of bond in N2 molecule is
Triple covalent bond, and that is why it is hardly reactive because in order to react you must break three strong covalent bonds.
Abdelkarim
what is electromagnetic energy
in a school of 120 students, 41studied mathematics, 48studied chemistry and 42 studied physics, 16 studied both chemistry and mathematics, 14 studied mathematics and physics, 18 studied chemistry and physics and 9 studied all the three subjects. how many of them studied exactly one subject?
Does Chromium oxidize?
yes
Alaa
@Alaa It doesn't.
Jag
yes. it's a very strong oxidizing agent
xMah_Bx
what is compound
what are the types of hydrocarbon
homologous series is under what
Dolapo
Don't get your Question.
Jag
OK Aliphatic and Aromatic.
Jag