What are Acids and Bases?

ACIDS

Acids are those substances which have a sour taste and can turn blue litmus red.

BASES

Bases are those substances which have a bitter taste and can turn red litmus blue.

ARRHENIUS CONCEPT

An acid is any hydrogen containing compound which gives H⁺ ion in aqueous solution.

While, base gives OH^– in aqueous solution.

For eg,

All the above 3 examples contain H⁺, thus they are acids in nature.

BRONSTED LOWRY THEORY

Any acid is defined as any hydrogen containing material that can donate a proton to any other substance.

Whereas, base is any substance that can accept a proton from any other substance.

CONJUGATE ACID BASE PAIR

WHAT ARE CONJUGATE ACID BASE PAIR?

• Pairs which can be formed from each other mutually by the gain or loss of proton.
• The stronger acid and weaker base form one conjugate acid base pair and weaker acid and stronger base form another pair.

LEWIS CONCEPT

• An acid is any species that can accept an electron pair to form coordinate covalent bond.
• A base is any species that can donate an electron pair in the formation of coordinate bond.

   What is pH?

pH refers to the power of the H⁺ concentration. pH value is also an indicator of the acidity or basicity. Its value ranges from 0 to 14. If the value of any compound in solution comes 0, means the pH is neutral. However, if the value is greater than 0 and lesser than 7, then the pH is acidic. If the value is greater than 7 and lesser than 14, then the pH is basic.

If acidity pH is far from the neutral pH then the acid is STRONG and if the value of pH is close to the neutral pH i.e. 7, means the acid is WEAK.

If basicity pH is far from 7, means it is a STRONG base and if the values are close to the neutral pH, it signifies the WEAK base.

pH now-a-days is measured by the pH meter.

Q.1. According to Bronsted Lowry Theory, Acid is a substance that can:

1. Accept a proton
2. Donate a proton
3. Both
4. None

Ans. b

Q.2. According to Bronsted Lowry Theory, Base is a substance that can:

1. Accept a proton
2. Donate a proton
3. Both
4. None

Ans. a

Q.3. Acid turn:

1. Blue litmus red
2. Red litmus blue
3. Both
4. None

Ans. a

Q.4. Base turn:

1. Blue litmus red
2. Red litmus blue
3. Both
4. None

Ans. b

Q.5. According to Arrhenius concept, acid gives ____ion in the aqueous solution.

1. H⁺
2. OH^–
3. Both
4. None

Ans. a

Q.6. According to Arrhenius concept, base gives ____ion in the aqueous solution.

1. H⁺
2. OH^–
3. Both
4. None

Ans. b