Notes on Three Theories of Acids and Bases

There are three primary theories that explain the behavior of acids and bases: Arrhenius Theory, Bronsted-Lowry Theory, and Lewis Theory. Each theory provides a different perspective and expands upon the definitions of acids and bases.

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1. Arrhenius Theory

Definition:
- Proposed by Svante Arrhenius in the late 19th century.
- Defines acids and bases based on their behavior in water.

🔑Key Points:
- Arrhenius Acid: A substance that increases the concentration of hydrogen ions (H^+) in aqueous solution.
- Example: Hydrochloric acid (HCl):

HCl → H^+ + Cl^-


- Arrhenius Base: A substance that increases the concentration of hydroxide ions (OH^-) in aqueous solution.
- Example: Sodium hydroxide (NaOH):

NaOH → Na^+ + OH^-


Limitations:
- Only applies to aqueous solutions and cannot explain acid-base reactions that occur in non-aqueous solvents.
- Does not account for substances that can act as acids or bases but do not contain H^+ or OH^-.

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2. Bronsted-Lowry Theory

Definition:
- Developed by Johannes Nicolaus Bronsted and Thomas Martin Lowry in 1923.
- Defines acids and bases based on their ability to donate or accept protons (hydrogen ions).

Key Points:
- Bronsted-Lowry Acid: A proton donor.
- Example: Acetic acid (CH_3COOH):

CH_3COOH ⇌ H^+ + CH_3COO^-


- Bronsted-Lowry Base: A proton acceptor.
- Example: Ammonia (NH_3):

NH_3 + H^+ ⇌ NH_4^+


Advantages:
- Applies to a broader range of acid-base reactions, including non-aqueous solutions.
- Explains the behavior of many substances that do not fall under the Arrhenius definition.

Limitations:
- Does not account for acid-base reactions that do not involve proton transfer.

3. Lewis Theory

Definition
- Introduced by Gilbert N. Lewis in 1923.
- Defines acids and bases in terms of electron pair acceptance and donation.

🔑 Key Points:
- Lewis Acid: An electron pair acceptor.
- Example: Boron trifluoride (BF_3), which can accept an electron pair from ammonia.

- Lewis Base: An electron pair donor.
- Example: Ammonia (NH_3), which can donate a pair of electrons to BF_3:

BF_3 + NH_3 → F_3B ⋯ NH_3


Advantages
- Provides a more comprehensive definition that includes all acid-base reactions involving electron transfer.
- Covers coordination chemistry and reactions that do not involve protons.

Limitations:
- Some may find the definitions more abstract and less intuitive compared to the other theories.

👉 Summary

Understanding these three theories of acids and bases enhances your knowledge of chemical reactions and interactions. Each theory builds on the previous one, offering broader definitions and applications:

- Arrhenius Theory focuses on H^+ and OH^- in water.
- Bronsted-Lowry Theory introduces proton donation and acceptance.
- Lewis Theory expands the definitions to include electron pair interactions
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Physics multiple choice questions and answers

1.Light year is a unit of _
a)time
b) light
c)intensity of light
d) distance

Answer d

2.The speed of light will be minimum while passing through  ___
a) water
b)air
c)vacuum
d)glass

Answer d

3.The stars appear to move from east to west because
a) The earth rotates from east to west
b) The earth rotates from west to east
c) All stars move from east to west
d) The background of the stars moves from west to east.

Answer b

4.RADAR is used for what?
a) receiving a signal in a radio receiver
b) locating submerged submarines
c) locating geostationary satellites
d) detecting and locating the position of objects such as Aeroplanes

Answer d

5. Sound waves in air are
a) electromagnetic
b) longitudinal
c) polarized
d) transverse

Answer b

6. Metals are good conductors of electricity because  _
a) They have a high melting point
b) The atoms are lightly packed.
c) They contain free electrons
d) All of the above.

Answer c

7.Rainbow is due to
a) refraction and reflection of sunlight by water droplets
b) absorption of sunlight in minute water droplets
c) diffusion of sunlight through water droplets
d) ionization of water deposit.   

Answer a

8.The optical fibers work on the  _
a)total internal reflection
b) principle of refraction
c) interference
d) scattering

Answer a


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