Acids, bases, and salts are fundamental concepts in chemistry that are often studied together. Understanding the properties and behavior of these substances is essential in various chemical reactions and their applications in daily life. Let's delve into the concepts of acids, bases, and salts and explore some previous year questions with solutions related to these topics.

Acids:
Acids are substances that release hydrogen ions (H+) when dissolved in water. They have a sour taste and can react with metals to produce hydrogen gas. Some common examples of acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), and acetic acid (CH3COOH). Acids are characterized by the presence of a low pH value (below 7), turn blue litmus paper red, and have a corrosive nature.

Bases:
Bases, also known as alkaline substances, are the opposite of acids. They are substances that release hydroxide ions (OH-) when dissolved in water. Bases have a bitter taste, feel slippery to touch, and can neutralize acids. Some common examples of bases include sodium hydroxide (NaOH), potassium hydroxide (KOH), and ammonia (NH3). Bases have a high pH value (above 7), turn red litmus paper blue, and have a soapy texture.

Salts:
Salts are ionic compounds formed by the reaction between an acid and a base. They are composed of cations (positively charged ions) and anions (negatively charged ions). The cation is usually derived from a base, while the anion is derived from an acid. The combination of these ions results in a neutral compound with no acidic or basic properties. Some examples of salts include sodium chloride (NaCl), calcium carbonate (CaCO3), and potassium nitrate (KNO3).

Previous Year Questions:
1. What is the pH value of a neutral solution?
Solution: The pH value of a neutral solution is 7.

2. Which gas is evolved when an acid reacts with a metal?
Solution: Hydrogen gas (H2) is evolved when an acid reacts with a metal.

3. How does the concentration of hydronium ions (H3O+) change when an acidic solution is diluted?
Solution: The concentration of hydronium ions decreases when an acidic solution is diluted.

4. How can you differentiate between a weak acid and a strong acid?
Solution: A weak acid only partially dissociates in water and has a lower concentration of hydronium ions. On the other hand, a strong acid fully dissociates in water and has a higher concentration of hydronium ions.

5. What happens when an acid reacts with a base? Provide an example.
Solution: When an acid reacts with a base, they neutralize each other to form a salt and water. For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), sodium chloride (NaCl) and water (H2O) are formed.

In conclusion, acids, bases, and salts are essential concepts in chemistry. Understanding their properties, behavior, and reactions is crucial in various chemical processes and applications. By studying previous year questions with solutions, one can gain a deeper understanding of these topics and excel in their studies.