Acids and bases are the foundation of chemistry — from the sour taste of lemons to the slippery feel of soap, their reactions shape our daily life. But have you ever wondered why some substances act as acids and others as bases? Scientists have explained this behavior using three famous theories: the Arrhenius, Bronsted–Lowry, and Lewis concepts.
In this detailed blog by Learn Chemistry by Inam Jazbi, you’ll learn the 3 main concepts of acids and bases with easy definitions, examples, and a comparison table — all explained in a way that’s simple, clear, and perfect for MDCAT, FSc, and O-Level students.
Different concepts of Acids and Bases
Hydronium and Hydroxyl Ions
Hydrogen ion by itself is a bare proton with extremely small size (~10–15 m or 10–13 cm radius, comparing other ions which have diameters of the order of 10–8 cm) having intense electric field and very high charge density. Therefore, hydrogen ion cannot exist in water or any other solvent.
Hydrogen ion binds itself with the water molecule at one of the two available lone pairs on it giving H3O+ ion which is called hydroxonium or hydronium or oxonium ion. This species has been detected in many compounds (e.g. H3O+Cl–) in the solid state. In aqueous solution the hydronium ion is further hydrated to give species like
Similarly the hydroxyl ion is hydrated to give several ionic species like H3O2–, H5O3– and H7O4– etc.
Introduction
A broader, more general and Protonic definition of acids and bases were proposed independently by the Danish Chemist Johannes Bronsted and the English Chemist Thomas M. Lowry in 1923 on the basis of proton-transfer.
Definition
According to Bronsted-Lowry theory, an acid is a
substance that is capable of donating a hydrogen ion (H+) or proton to another substance
and a base is a substance capable of accepting a hydrogen ion (H+)
or proton from another substance. Hence, In short, acids are proton donors and bases are proton acceptors. For example, HCl acts as an acid while NH3 acts as a base. All
Arrhenius acids are Bronsted acids but but except OH− other Bronsted bases are not Arrhenius bases.
OR
In other words, an acid is a substance that gives oxonium ion or hydroxonium ion (H3O+) in aqueous solution by donating H+ ions. a base is a substance that combines or adds with proton of oxonium ion (H3O+) or conjugate acid accepting or removing a proton forming water water or OH- ion i.e. accepts).
According to this concept, acid-base pairs i.e. proton donor and proton acceptor must co-exist. Thus an acid and a base always work together to transfer a proton. Stated differently, no substance can act as an acid in solution unless a base is present to accept a proton i.e. the reactions of acids are reaction between acids and bases. Similarly, all reactions of bases in solution are acid-base reactions. The products of acid-base reaction are themselves acids and base which are called conjugate acids and conjugate base respectively.
amphoteric or amphiprotic
substances
Some substances can act as proton donor as well as proton abstractor and are called amphoteric or amphiprotic. i.e. they
can behave as an acid, as well as, a base e.g. H2O,
According to Bronsted-Lowry concept, an acid and a base always work together to transfer a proton. That means, a substance can act as an acid (proton donor) only when another substance simultaneously behaves as a base (proton acceptor). Hence, a substance can act as an acid as well as a base, depending upon the nature of the other substance.
General Example
Consider the dissociation reaction of a general monoprotic acid HA in water in which HA dissolves in water in a reversible manner by donating
a proton to water. Therefore, HA is the Bronsted-Lowry acid and H2O is the Bronsted-Lowry base. It is seen that the products of
acid-base reaction (H3O+ and A-) are
themselves acids and bases which are called conjugate acid and conjugate
base respectively.
In
each acid-base reaction an acid reacts with a base to give a conjugate base and
a conjugate acid.
Example # 1 of Bronsted-Lowry
Concept
When hydrogen chloride is dissolved in
water, a reversible reaction takes place called ionization. In this reaction,
HCl donates its one proton to water acting as a Bronsted acid giving Cl– ion while water accepts that
one proton acting as a Bronsted base forming hydronium (H3O+)
ion. H3O+ is called conjugate acid and Cl– is a conjugate base. The products of this reaction are
themselves acid and base which are called conjugate acid and conjugate base
respectively].
Example # 2 of Bronsted-Lowry
Concept
Consider the
dissolution of acetic acid (CH3COOH) in water. In the forward
reaction, acetic acid is a Bronsted acid as it donates its one proton to water
while water is a Bronsted base as it accepts a proton. Like this we have pairs
of conjugated acids-base pairs. Conjugate acid is formed by accepting a proton
by a base and conjugate base is produced by donating a proton by an acid.
Example # 3 of Bronsted-Lowry
Concept
Example # 4 of Bronsted-Lowry
Concept
Conjugate Acid-Base Pair
Acids and bases occur as conjugate acid-base pair (the word conjugate means “joined together or tie together as a pair”) which are defined as
an acid and a base that differ only in the presence or absence of a proton or pair of acid and base that are related to each other by loss or gain of a proton.
Conjugate Base
Every acid has a conjugate base which is the negatively charged or neutral specie formed by the removal or release of a proton from the acid. A conjugate base is a species that results when an acid loses a proton.
Conjugate Acid
Every base is associated with a conjugate acid which is the positively charged ion produced by the acceptance or addition of a proton by a base. The species that results when a base accepts a proton from an acid is called the conjugate acid.
1. According to this concept, proton donor and proton acceptor must co-exist. But there are many reactions in which this does not happen.
2. It also could not explain the behaviour of those acids and bases which do not contain hydrogen at all having no tendency to lose H+ ions i.e. it does not explain acidic behaviour of aprotic acids like SO2, SO3, CO2, AlCl3, SiCl4 etc. e.g. SO3 behave as an acid although it does not have the ability to donate a proton. CaO behaves as a base but it cannot accept a proton.
3. It could
not explain the basic nature compounds having OH- ions e.g. NaOH,
KOH, Ca(OH)2
Significance
AlCl3, BF3, BCl3, ZnCl2, FeCl3 are considered as acids although they do not have hydrogen. In 1923, an American Chemist G.N. Lewis proposed a more general and broader electronic concept of acids and bases focusing on electron transfer instead of proton transfer. Lewis concept can be applicable to non-aqueous solutions or solutions lacking hydrogen ions and reactions that do not involve hydrogen ions at all. The Lewis definition is much more useful than the others because it can be applied to all species and reaction. The other definitions are only useful for species and reactions involving H+.
Lewis Definition of Acid and Base
In the Lewis theory of
acid-base reactions, bases donate pairs of electrons and
acids accept pairs of electrons. A Lewis acid is any substance, such as the H+ ion,
that can accept a pair of nonbonding electrons i.e. a
Lewis acid is an electron-pair acceptor.
A Lewis base is
any substance, such as the OH- ion, that can donate a pair of non-bonding electrons i.e. A Lewis
base is an electron-pair donor.
A Lewis acid must have a vacant orbital into which it can accept the electron pair. H+ is a Lewis acid. A Lewis acid-Lewis base reaction gives Lewis adduct. Lewis acid-base reactions in general do not have to involve H+
Lewis Definition of Acid
An acid is any species (molecule or ion) which can accept a (lone) pair of electrons during a reaction i.e. Lewis Acids are an electron-pair acceptor. They are also called Electrophiles (meaning electron loving) and have vacant orbitals into which it can accept the electron pair.
Lewis acids include not only H+ (protons) or H3O+ (oxonium ion) but also other cations and neutral molecules having vacant valence orbitals like AlCl3, AlBr3, BF3, BCl3, ZnCl2, FeCl3 etc.
Example # 1 of Lewis Acid and Base
Consider the reaction between proton and water. The proton (H+) has a tendency to accept a pair of electrons while H2O has a tendency to donate a pair of electrons to form coordinate covalent bond or
donor-acceptor bond. Hence in Lewis concept, H+ is a Lewis acid and H2O is a Lewis base.
Example # 2 of Lewis Acid and Base
H+ ion acts as Lewis acid because it is short of two electrons for completion of its duplet and thus capable of accepting a lone pair of electrons from N of ammonia which is a Lewis base making co-ordinate covalent bond.
Example # 3 of Lewis Acid and Base
Consider the reaction between Nh3
and BF3. Here NH3 acts as an electron pair donor and
hence it is Lewis base while BF3 acts as an electron pair acceptor
and hence it is Lewis acid and they combine to form adduct through coordinate
covalent bond.
Lewis Definition
of Base
A base is any species (molecule or ion) which can donate a (lone) pair of electrons during a reaction i.e. Lewis bases are electron pair donor. They are also called Nucleophiles (meaning nucleus loving) and have lone pair of electrons.
Lewis bases include not only OH– ions but also all anions (F–, Cl– etc) and neutral molecules having lone pair of electrons (NH3, C2H5OH etc.). Ammonia is base in all three concepts.
Example # 5 of Lewis Acid and Base
ammonia is a Lewis base as it donates its an electron pair to boron of
boron trifluoride lacking a pair of electrons to complete its octet acting as
Lewis acid to form co-ordinate covalent bond.
Example # 6 of Lewis Acid and Base
Chloride ion is a Lewis base as it donates its an electron pair to aluminium
of aluminium trichloride lacking a pair of electrons to complete its octet
acting as Lewis acid to form co-ordinate covalent bond.
🧑🔬💡Types of Lewis Acids
1. All Metals cations e.g. Li+,
Ag+, Al3+, Mg2+ etc. and proton
itself act as Lewis acids.
2.
Molecules having incomplete octet e.g. BF3,
BCl3, AlCl3, B(OH)3 or H3BO3,
etc.
3.
Molecules having multiple bonds between
atoms of different E.N e.g. CO2, SO2, SO3 etc.
4. Molecules having vacant d-orbitals e.g. FeCl3, SF4, SF6, SnCl2, SnCl4 etc.
(i) Simple cations can act as Lewis acids. All cations act as
Lewis acids since they are deficient in electrons. However, cations such as Na+,
K+, Ca2+,
(ii) Molecules in which the central atom
has incomplete octet are always Lewis acids. For example, in BF3,
AICl3, FeCl3, the central atoms have only six electrons
around them, therefore, these can accept an electron pair.
🧑🔬💡Types or Examples of Lewis Bases
1. All anions e.g. chloride (Cl-), cyanide (CN-), hydroxide
(OH-), O2-,
2. Neutral
molecules having lone
(unshared) pair of electrons e.g. NH3, H2O , R-NH2, R2NH,
ROR etc.
3. pi-electrons containing Molecules being electron rich are Lewis bases e.g. alkenes,
alkynes, benzene
Neutral species having at least one lone pair of electrons act as Lewis bases. For example, ammonia, amines, alcohols etc. act as Lewis bases as they contain a lone pair of electrons:
The
cations (proton itself or metal ions) act as Lewis acids.
The product
of any Lewis acid-base reaction is a single specie, called an adduct. So, a
neutralization reaction according to Lewis concept is donation and acceptance
of an electron pair to form a coordinate covalent bond in an adduct.
Acids are electron pair acceptors while bases are electron pair donors. Thus, it is evident that any substance which has an unshared pair of electrons can act as a Lewis base while a substance which has an empty orbital that can accommodate a pair of electrons acts as Lewis acid.
All the
Lewis bases are Bronsted bases but all the Lewis acids are not Bronsted acids
It may be noted that all Bronsted bases are also Lewis
bases but all Bronsted acids are not Lewis
acids.
According to Bronsted concept, a base is a substance which can accept a proton,
while according to Lewis concept, a base is a substance which can donate a pair
of electrons. Lewis bases generally contain one or more lone pair of electrons
and therefore, they can also accept a proton (Bronsted base). Thus, all Lewis
bases are also Bronsted bases. On the other hand, Bronsted acids are those
which can give a proton. For example, HCI, H2SO4 are not
capable of accepting a pair of electrons. Hence, all Bronsted acids are not
Lewis acids.
🧪 Summary of 3 Powerful Concepts of Acids and Bases Explained Simply | Learn Chemistry by Inam Jazbi
🔍 Introduction
Acids and bases are among the most fascinating topics in chemistry. From lemon juice to soaps, almost every chemical reaction around us depends on whether a substance behaves as an acid or a base. Scientists have proposed three main concepts to define acids and bases: Arrhenius, Bronsted–Lowry, and Lewis theories. Understanding these gives you a complete picture of acid–base behavior in both aqueous and non-aqueous systems.
⚗️ 1. Arrhenius Concept of Acids and Bases
📘 Definition
Proposed by Svante Arrhenius (1884), this theory applies to aqueous solutions only.
🔑Acid: A substance that produces H⁺ ions in water.🔑Base: A substance that produces OH⁻ ions in water.
🧩 Examples
- HCl (aq) → H⁺ + Cl⁻ → acid
- NaOH (aq) → Na⁺ + OH⁻ → base
💡 Limitations
- Works only in aqueous media.
- Cannot explain acid–base behavior in non-aqueous solvents.
- Fails to explain why NH₃ acts as a base (no OH⁻ ions).
⚗️ 2. Bronsted–Lowry Concept of Acids and Bases
📘 Definition
Proposed by Johannes Bronsted and Thomas Lowry (1923), this concept defines acids and bases in terms of proton transfer.
🔑Acid: Proton (H⁺) donor🔑Base: Proton (H⁺) acceptor
🧩 Example
NH₃ + H₂O ⇌ NH₄⁺ + OH⁻
- NH₃ → Base (accepts H⁺)
- H₂O → Acid (donates H⁺)
- NH₄⁺ and OH⁻ form a conjugate acid–base pair
💡 Key Points
⚡Explains acid–base behavior in non-aqueous systems.⚡Introduces the idea of conjugate acid–base pairs.
⚡Limited to reactions involving proton transfer.
⚗️ 3. Lewis Concept of Acids and Bases
📘 Definition
Proposed by G. N. Lewis (1923), this theory focuses on electron pair transfer rather than protons.
🔑 Lewis Acid: Electron pair acceptor🔑 Lewis Base: Electron pair donor
🧩 Examples
🔍 NH₃ + BF₃ → H₃N–BF₃NH₃ donates an electron pair → Lewis base
BF₃ accepts an electron pair → Lewis acid
🔍H⁺ + :OH⁻ → H₂O
H⁺ = Lewis acid
OH⁻ = Lewis base
💡 Importance
⚡Most general and widely applicable acid–base concept.
⚡Used in organic and coordination chemistry.
📊 Comparison Table of the Three Concepts
| Feature | Arrhenius | Bronsted–Lowry | Lewis |
|---|---|---|---|
| Basic Idea | Ionization in water | Proton transfer | Electron pair transfer |
| Medium | Only aqueous | Aqueous & non-aqueous | Any medium |
| Acid | H⁺ producer | Proton donor | Electron pair acceptor |
| Base | OH⁻ producer | Proton acceptor | Electron pair donor |
| Examples | HCl, NaOH | NH₃, H₂O | BF₃, NH₃ |
🧠 Quick Revision Tips
⚡Arrhenius – Ions⚡Bronsted–Lowry – Proton
⚡Lewis – Electrons
⚡Arrhenius is simplest, Lewis is most general.
⚡Practice examples from inorganic & organic chemistry.
💧 MDCAT Style MCQs on Acids, Bases, and Salts | Learn Chemistry by Inam Jazbi
Test your knowledge of acids, bases, and salts with these MDCAT-style multiple choice questions. Each question includes a brief explanation for better understanding.
1. Which of the following is an Arrhenius acid?
A) NaOH
B) NH₃
C) HCl
D) K₂CO₃
Explanation: Arrhenius acids release H⁺ ions in water. For example, HCl → H⁺ + Cl⁻.
2. Which of the following acts as a Bronsted–Lowry base?
A) H₂SO₄
B) NH₃
C) HCl
D) H₂O
Explanation: A Bronsted–Lowry base is a proton (H⁺) acceptor. NH₃ accepts H⁺ from water to form NH₄⁺.
3. Which of the following is a Lewis acid?
A) NH₃
B) BF₃
C) OH⁻
D) H₂O
Explanation: A Lewis acid accepts an electron pair. BF₃ can accept an electron pair from NH₃.
4. Which salt is formed when HCl reacts with NaOH?
A) KCl
B) NaCl
C) NH₄Cl
D) Na₂SO₄
Explanation: HCl + NaOH → NaCl + H₂O. Neutralization produces a salt and water.
5. Which of the following pairs is a conjugate acid–base pair?
A) H₂SO₄ / SO₄²⁻
B) NH₄⁺ / NH₃
C) HCl / Cl₂
D) NaOH / H₂O
Explanation: A conjugate acid–base pair differs by one proton. NH₄⁺ donates H⁺ to form NH₃.
6. Which of the following is a basic salt?
A) NaCl
B) CH₃COONa
C) NH₄Cl
D) KNO₃
Explanation: CH₃COONa is formed from a weak acid (CH₃COOH) and a strong base (NaOH), making it basic.
7. Which solution has a pH less than 7?
A) NaOH
B) H₂SO₄
C) Na₂CO₃
D) KOH
Explanation: Acids have pH < 7. H₂SO₄ is a strong acid producing many H⁺ ions.
8. Which salt solution is acidic?
A) NH₄Cl
B) Na₂CO₃
C) KCl
D) NaCl
Explanation: NH₄Cl is formed from a weak base (NH₃) and strong acid (HCl), so its solution is acidic.
9. Which of the following acids is diprotic?
A) HCl
B) H₂SO₄
C) HNO₃
D) CH₃COOH
Explanation: Diprotic acids can donate 2 protons. H₂SO₄ → 2H⁺ + SO₄²⁻.
10. What is the product of neutralization between HNO₃ and KOH?
A) K₂SO₄
B) KNO₃
C) NH₄NO₃
D) NaNO₃
Explanation: Acid + Base → Salt + Water. HNO₃ + KOH → KNO₃ + H₂O.
✨ Quick Tip by Inam Jazbi
Remember: Acids donate H⁺, Bases accept H⁺, and Salts form from neutralization. Practice these MCQs to strengthen your MDCAT chemistry preparation.
Textbook MCQs on Acids, Bases and Salts
1.
H2SO4 is stronger acid than CH3COOH because:
(a) It gives two H+ ion per molecule
(b) Its boiling point is high
(c) Its degree of ionization is high
(d) It is highly corrosive
Explanation (Answer; c)
The strength of an acid depends upon its degree of ionization and acid ionization constant (Ka). Greater the value of degree of ionization (equal or greater than 30%) and Ka (more than 10−3), stronger is the acid. The degree of ionization of H2SO4 is quite high about 60% (first step) and its Ka is also quite high about 103 (Ka2 for HSO4− = 1.3 x 10−2) showing that it is a very strong acid. Contrarily, The degree of ionization of CH3COOH is quite low about 1.4% and its Ka is also quite low about 1.7 x 10−5 showing that it is a weaker acid than H2SO4.
2.
Which of the following statements is not correct about the bases?
(a) They have bitter tastes
(b)
They have high pH value
(c) They react with acids to form salts
(d) They turn blue litmus red
Explanation (Answer; d)
Bases turns red litmus paper blue.
3.
Al2O3 is amphoteric oxide because it reacts with:
(a) Acids
(b) neither acid nor base
(c) Both acids and base
(d) Base
Explanation (Answer; c)
amphoteric oxides have dual characteristics of acid and base
and hence they react both with acid and base through neutralization forming
salt and water.
The oxides of amphoteric metals like Be, Al, Sn, Pb, Zn, Cr etc. are amphoteric . These oxides react with both acids and base via neutralization to form salt and water. Al2O3, ZnO, BeO, SnO, SnO2, PbO, PbO2, Cr2O3 are amphoteric oxides.
4.
Which of the following is not a
buffer solution?
(i) Na2CO3 /NaHCO3
(b) CH3COOH/CH3COONa
(c) NH4OH/NH4Cl
(d) NaOH/HCl
Explanation (Answer; d)
Buffer solution is a mixture of weak acid and its salt with strong base or weak base and its salt with strong base. In option ‘d’, NaOH and HCl are both base and acid.
5.
Which oxide is amphoteric in nature:
(a) K2O
(b) CO2
(c) CaO
(d)
Al2O3
Explanation (Answer;
d)
The oxides of amphoteric metals like Be, Al, Sn, Pb, Zn, Cr etc are amphoteric . These oxides react with both acids and base via neutralization to form salt and water. Al2O3, ZnO, BeO, SnO, SnO2, PbO, PbO2, Cr2O3 are amphoteric oxides.
The oxides of metals like K2O,
Li2O, Na2O, MgO, CaO, BaO etc. are basic.
The oxides of non-metals like CO2, SO2, SO3, NO2, N2O5, P2O3, P2O5, Cl2O, Cl2O7 etc. are acidic. (Some non-metallic oxides like H2O, N2O, NO and CO are neutral).
6.
Which of the following does not alter the pH of a solution?
(a) NH4Cl
(b) Na2CO3
(c) NaCl
(d)
Mg(OH)Cl
Explanation (Answer;
c)
Neutral salts formed from strong acids and strong bases like NaCl, KBr, KCl, BaCl2, Na2SO4, KNO3 etc. do not change the pH of solution.
7.
Conjugated acids of NH3 is:
(a) NH4+
(b) NH2-
(c) NH2
(d)
NH
Explanation (Answer;
a)
To form conjugate acid from a
compound or ion, just add H into it while to form conjugate base of a compound
or ion just remove H from it. Don’t forget to balance charge either adding or
subtracting H. Addition of H increases one unit + charge while removing of H
decreases one + charge.
NH3 (adding add H into
it will introduce + charge) …………… NH4+ (conjugate acid)
NH3 (removing H from it will introduce – charge) ……………. NH2− (conjugate base)
8.
Salt which is formed by the neutralization of weak acid and strong base is:
(a) NaNO3
(b) NH4Cl
(c) Na2CO3
(d) NH4CN
Explanation (Answer;
c)
Strong bases contain Na+, K+, Ba2+ as cation while weak acids contains anions other than Cl−, Br−, I−, NO3−, SO4−, ClO4−, and ClO3−. A salt formed from weak acid and strong base via neutralization contains any one of the cation like Na+, K+, Ba2+ and anion other than Cl−, Br−, I−, NO3−, SO4−, ClO4−, and ClO3−. Sodium carbonate (Na2CO3) is a salt derived from the neutralization of weak acid (H2CO3 containing CO32− anion) and strong base (NaOH).
9.
A conjugate acid base pair has the difference of only:
(a) One electron
(b) One proton
(c) One electron pair
(d)
One proton pair
Explanation (Answer;
b)
conjugate acid-base pair differs from one another only by a single proton (H+). To identify a conjugate acid base pair, we look at the specie that donates a proton and the specie that is formed from it by the loss of proton. In the given reaction, NH3 accepts a proton acting as a Bronsted base to form NH4+ which is its conjugate acid. Similarly, HCl donates a proton acting as a Bronsted acid to form Cl− which is its conjugate base.
10.
Salt formed by neutralization of weak acid and weak base is:
(a) NH4Cl
(b) Na2CO3
(c) NH4CN
(d)
Na2SO4
Explanation (Answer;
c)
Strong bases contain Na+, K+, Ba2+ as cation while weak acids contains anions other than Cl−, Br−, I−, NO3−, SO4−, ClO4−, and ClO3−. A salt formed from weak acid and weak base via neutralization contains any cation other Na+, K+, Ba2+ and any anion other than Cl−, Br−, I−, NO3−, SO4−, ClO4−, and ClO3−. Ammonium cyanide (NH4CN) is a salt derived from the neutralization of weak acid (HCN containing CN− anion) and weak base (NH4OH).
Newly Compiled Textbook MCQs on Acids, Bases and Salts
1. The aqueous solution of
KCl is:
(a) Neutral
(b) Acidic
(c) Basic
(d) Alkaline
Explanation (Answer;
a)
2 Which one of the
following yield basic solution?
(a) Copper sulphate
(b) Ammonium chloride
(c) Soda acetate.
(d)
Sliver nitrate
Explanation (Answer;
c)
3. Universal indicator
turns red in:
(a) Neutral solution
(b) Alkaline solution
(c) Acid solution
(d) Basic solution
Explanation (Answer;
c)
4. Which one of the
following is not a strong acid?
(a) HF
(b) HNO3
(c) HCl
(d) H2SO4
Explanation (Answer;
a)
5. Which one of the
following substances has pH value more than 7?
(a) Vinegar
(b) Sodium carbonate
(c) Sulphuric acid
(d) Soda water
Explanation (Answer;
b)
6. Which one of the
following is not a salt of weak
acids and strong bases?
(a) Sodium ethanoate
(b) Potassium cyanide
(c) Ammonium chloride
(d) Sodium
carbonate
Explanation (Answer;
c)
7. Which one of the
following is not a salt of strong
acids and weak bases?
(a) Copper(II) sulphate
(b) Ammonium chloride
(c) Sodium acetate
(d) Ferric chloride
Explanation (Answer;
c)
8. Which one of the
following salts dissolves in water to produce a solution with pH less than 7?
(a) Sodium ethanoate
(b) Borax
(c) Bleach
(d) None of them
Explanation (Answer;
d)
9. Which one of the
following salts dissolves in water to produce a solution with pH more than 7?
(a) Ammonium nitrate
(b) Ferric chloride
(c) Sodium sulphate
(d) None of
them
Explanation (Answer;
d)
10. Which of the following salts has no water of crystallization?
(a) Gypsum
(b) Blue vitriol
(c) Baking soda
(d)
Washing soda
Explanation (Answer;
c)
11. Which ion is not present
in dilute sulfuric acid?
(a) H+
(b) OH–
(c) SO32–
(d) SO42–
Explanation (Answer;
c)
12. Which salt is NOT
derived from a strong acid and a strong soluble base?
(a) MgCl2
(b) LiClO4
(c) NaI
(d) CsBr
Explanation (Answer;
a)
13. The aqueous solution of
NaCl is:
(a) Neutral
(b) Acidic
(c) Basic
(d) Alkaline
Explanation (Answer;
a)
14. Which one of the
following yield basic solution?
(a) Copper sulphate
(b) Ammonium chloride
(c) Potassium cyanide
(d) Sliver nitrate
Explanation (Answer;
c)
15. Universal indicator
turns green in:
(a) Neutral solution
(b) Alkaline solution
(c) Acid solution
(d)
Basic solution
Explanation (Answer;
a)
16. NH3 can be a base according to
(a) Arrhenius theory
(b) Bronsted-Lowry theory
(c) Lewis theory
(d) both b and c
Explanation (Answer;
d)
17. Which of the following is a Lewis base?
(a) HNO3
(b) CN−
(c) HCl
(d) AlCl3
Explanation (Answer;
b)
18. A
substance that can donate a pair of electrons to form coordinate covalent bond
(a) Lewis acid
(b) Bronsted Lowry acid
(c) Bronsted-Lowry base
(d)
Lewis base
Explanation (Answer;
d)
19. If
pH value is greater than 7, then solution is
(a) acidic
(b) basic
(c) amphotetic
(d) neutral
Explanation (Answer;
b)
20. Which of the following
is an acid-base conjugate pair?
(a) HClO and Cl–
(b) HNO2 and NO3–
(c) H2CO3 and CO32–
(d) HF and F–
Explanation (Answer;
c)
21. What
will be the pH of aqueous solution of NH4Cl?
(a) pH = 7
(b) pH = 0
(c) pH > 7
(d) pH < 7
Explanation (Answer;
d)
22. Which one of the
following is non-hydrolyzable salt?
(a) Na2CO3
(b) NaCl
(c) AlCl3
(d) CuSO4
Explanation (Answer;
b)
23. Aqueous solution of NaCl
has a pH
(a) 7
(b) Greater than 7
(c) Less than 7
(d) Zero
Explanation (Answer;
a)
24. Hydrolysis of potassium
acetate gives
(a) Basic solution
(b) Highly acidic solution
(c) Neutral solution
(d)
Acidic solution
Explanation (Answer;
a)
25. Aqueous solution of CuSO4
has a pH
(a) Greater than 7
(b) Less than 7
(c) Equal to 7
(d) Zero
Explanation (Answer;
b)
26. Which of the following phenomena will occur when a small
amount of acid is added to water?
(a) dilution
(b) neutralization
(c) ionization
(d) Both a and c
Explanation (Answer;
d)
27. Strong bases are
(a) Non-electrolytes
(b) strong electrolytes
(c) weak electrolytes
(d) also strong acids
Explanation (Answer;
b)
28. Whose definition of acids and bases emphasizes the role of
protons?
(a) Faraday
(b) Arrhenius
(c) Brønsted & Lowry
(d)
Lewis
Explanation (Answer;
c)
29. An electron-pair acceptor is a
(a) Lewis base
(b) traditional acid
(c) Lewis acid
(d) Brønsted base
Explanation (Answer;
c)
30. Which one of the given
is hydracid?
(a) HNO₃
(b) HCN
(c) H₂SO₄
(d) H₃PO₄
Explanation (Answer;
b)
31. Which element is always
present in Arrhenius acid?
(a) Nitrogen
(b) Hydrogen
(c) Oxygen
(d)
None of these
Explanation (Answer; b)
32. Ammonium sulphate salt
is
(a) Basic salt
(b) Complex salt
(c) Acidic salt
(d) Neutral salt
Explanation (Answer;
c)
33. Which of the following
does not form an acidic salt?
(a) Sulphuric acid
(b) Hydrochloric acid
(c) Phosphoric acid
(d)
Carbonic acid
Explanation (Answer;
b)
34 A Bronsted-Lowry base is
defined as:
(a) a hydroxide acceptor
(b) an electron pair acceptor
(c) a proton acceptor
(d) a
hydroxide donor
Explanation (Answer;
c)
35. The number of water
molecules attached to the ionic compounds depends upon………. of the ion.
(a) Electronegativity
(b) Electron affinity
(c) Charge density
(d) None of them
Explanation (Answer;
c)
36. Which one of the following
ions is readily hydrated?
(a) Al3+
(b) Mg2+
(c) Na1+
(d)All are equally hydrated
Explanation (Answer;
a)
37. Which of the following
is readily hydrated?
(a) Cations
(b) Anions
(c) Atoms
(d) All are
equally hydrated.
Explanation (Answer;
a)
38. The number of water
molecules attached to the ionic compounds depends upon………. of the ion.
(a) Charge of ion
(b) Size of ion
(c) Both of them
(d) None of them
Explanation (Answer;
c)
38.
(a) Weak acid and strong base
(b) Weak acid and weak base
(c) Strong acid and strong base
(d) Strong acid and weak base
Explanation (Answer;
a)
40. A salt X is dissolved in water of pH 7, the
resulting solution becomes acidic in nature, salt X is made up of
(a) Weak acid and strong base
(b)
Weak acid and weak base
(c) Strong acid and strong base
(d) Strong acid and weak base
Explanation (Answer;
d)
41. Which of the given is a
strong base?
(a) Calcium hydroxide
(b)
Magnesium hydroxide
(c) Ammonium hydroxide
(d) Potassium hydroxide
Explanation (Answer;
d)
42. An indicator is one kind
of the following compound
(a) Strong acid only
(b) Reducing
agent
(c) Weak base or acid only
(d) Complex salt
Explanation (Answer;
c)
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