Chemistry Notes on Acids and Base for Railways Exam

In this article, we have discussed the Acids and Bases for Railways Exams and various scientist theories which support the concept of acid and base. Generally, one question comes from this topic.

Organic Acids are those acids which are obtained from plants and animals. e.g. lactic acid, oxalic acid, acetic acid. Mineral Acids are those acids which are obtained from minerals.e.g. sulphuric acid and phosphoric acid.

Arrhenius concept of acids and bases:

• Acid is a substance which produces hydrogen ions (H⁺) in aqueous solution e.g. HCL (H⁺ Cl^-), Sulphuric Acid, H₂SO₄ (2H⁺ SO^2-₄).
• Base is a substance which produces Hydroxide ion (OH^-) in aqueous solution e.g. sodium hydroxide and ammonium hydroxide etc.

Bronsted Lowery concept of Acids and Bases

• An acid is a molecule or ion which is capable of donating a proton.
• A base is a molecule or ion which is capable of accepting a proton.

Lewis concept of Acids and Bases

• An acid is a substance which can accept an electron e.g. boron fluoride (BF₃) and carbon dioxide.
• Base is a substance which can produce an electron e.g. fluoride (F^-) and chloride (Cl^-).

Some important acids and their presence

These acids are mostly asked in SSC Exams. Don't forget to remember this table.

PH Scale

• PH value is a measure of the acidity or basicity of an aqueous solution.
• The solution with PH value less than 7 is considered as acidic.
• The solution with PH value greater than 7 is greater 7 is considered as basic.

PH values of some important solutions.

Buffer Solutions:

• The solutions which resist the change in its PH value on an addition of a small amount of acid or base are called buffer solutions.
• Acidic buffer solution has PH value less than 7.
• Basic buffer has PH value greater than 7.
• PH value of blood is maintained with the help of H₂CO₃/HCO₃ buffer inspite of many acidic foods we eat.

Salts:

• When acidic and basic solutions are mixed in proper proportion than their own nature is destroyed and Salt is formed.
• Acid turns blue litmus red and base turns red litmus blue.
• Formation of salts after mixing base and acidic is called a neutralisation reaction.

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