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Important Equations and Definitions: Acids, Bases and Salts | Science Class 10 PDF Download

Acids

Acids are substances that can donate protons (H+) or accept electron pairs.

  • Acids have a sour taste and turn blue litmus paper red.
  • Examples: Hydrochloric acid (HCl), Sulphuric acid (H2SO4), Nitric acid (HNO3), Acetic acid (CH3COOH).

Important Equations and Definitions: Acids, Bases and Salts | Science Class 10

Bases

Bases are substances that can accept protons (H+) or donate electron pairs.

  • Bases have a bitter taste and turn red litmus paper blue.
  • Examples: Sodium hydroxide (NaOH), Calcium hydroxide [Ca(OH)2], Potassium hydroxide (KOH), and Ammonium hydroxide (NH4OH).

Salt

A compound formed by the neutralization reaction between an acid and a base.

  • Hydrogen Ion (H+): Positively charged ion formed when an acid dissociates in water.
  • Hydroxide Ion (OH-): A negatively charged ion formed when a base dissolves in water.

Neutralization Reaction

Important Equations and Definitions: Acids, Bases and Salts | Science Class 10

  • A neutralization reaction occurs when an acid reacts with a base to form a salt and water.
  • General equation: Acid + Base → Salt + Water.

pH Scale

Important Equations and Definitions: Acids, Bases and Salts | Science Class 10

  • The pH scale measures the acidity or basicity of a solution.
  • pH values range from 0 to 14, with 7 being neutral, values below 7 indicating acidity, and values above 7 indicating basicity.

Litmus Paper: Litmus paper is a natural indicator that turns red in the presence of acids and blue in the presence of bases.

Olfactory Indicators: Olfactory indicators are substances whose odor changes in acidic or basic media. Examples: Vanilla, Onion, Clove.

Reaction of acids and bases with metals

Acids, in general, react with metals to produce salt and hydrogen gas. Bases, in general, do not react with metals and do not produce hydrogen gas.

1. Acid + active metal →  salt + hydrogen + heat

2HCl + Mg → MgCl2 + H2 (↑)
Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen

2. Base + metal → salt + hydrogen + heat

2NaOH + Zn → Na2ZnO2 + H2 (↑)
Sodium hydroxide + Zinc → Sodium zincate + Hydrogen

A more reactive metal displaces the less reactive metal from its base.

2Na + Mg (OH)2 → 2NaOH + Mg
Sodium + Magnesium hydroxide → Sodium hydroxide + Magnesium

Reaction of acids with metal carbonates and bicarbonates

Acid + metal carbonate or bicarbonate →  salt + water + carbon dioxide.
2HCl + CaCO3 → CaCl2 + H2O + CO2
H2SO4 + Mg (HCO3)2 → MgSO4 + 2H2O + 2CO2
Effervescence indicates the liberation of CO2 gas.

Reaction of Acid with Base

1. Reaction of metal oxides and hydroxides with acids

Metal oxides or metal hydroxides are basic in nature.

Acid + base → salt + water + heat

H2SO4 + MgO → MgSO+ H2O

2HCl + Mg (OH)2 → MgCl2 + 2H2O

2. Reaction of non-metal oxides with bases

Non-metal oxides are acidic in nature

Base + Nonmetal oxide →  salt + water + heat

2NaOH + CO2→ Na2CO3 + H2O

3. Reaction of acids and base

HCl (strong acid) + NaOH (strong base) → NaCl (salt) + H2O (water)

Water of Crystallisation

Fixed number of water molecules present in one formula unit of a salt.

For Example: CuSO4.5H2O Hydrated Copper Sulphate

Preparation of Bleaching Powder

Preparation Ca(OH)2(aq)+Cl2(g)→CaOCl2(aq)+H2O(l) 

Preparation of Washing Soda (Sodium hydrogen carbonate)

a. Limestone is heated: CaCO3→CaO+CO2
b. CO2 is passed through a concentrated solution of sodium chloride and ammonia:
NaCl(aq)+NH3(g)+CO2(g)+H2O(l)→NaHCO3(aq)+NH4Cl(aq) 

Equations:

Important Equations and Definitions: Acids, Bases and Salts | Science Class 10

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FAQs on Important Equations and Definitions: Acids, Bases and Salts - Science Class 10

1. What are acids and how are they defined in chemistry?
Ans. Acids are substances that can donate protons (H⁺ ions) in a solution. They typically have a sour taste and can turn blue litmus paper red. A common definition of an acid is based on the Brønsted-Lowry theory, which states that an acid is a proton donor.
2. What are bases and how do they differ from acids?
Ans. Bases are substances that can accept protons or donate hydroxide ions (OH⁻) in a solution. They usually have a bitter taste and can turn red litmus paper blue. The main difference between acids and bases is their ability to donate or accept protons; acids donate, while bases accept.
3. What is the pH scale and what does it measure?
Ans. The pH scale is a numerical scale that measures the acidity or basicity of a solution. It ranges from 0 to 14, with lower values indicating acidic solutions (pH < 7), a neutral value of 7 indicating pure water, and higher values indicating basic or alkaline solutions (pH > 7).
4. How do acids and bases neutralize each other?
Ans. Acids and bases neutralize each other through a chemical reaction that produces water and a salt. This occurs when the H⁺ ions from the acid react with the OH⁻ ions from the base, resulting in the formation of water (H₂O) and a salt derived from the acid and base used.
5. What are some common examples of acids, bases, and salts?
Ans. Common examples of acids include hydrochloric acid (HCl), sulfuric acid (H₂SO₄), and acetic acid (CH₃COOH). Common bases include sodium hydroxide (NaOH) and ammonia (NH₃). Salts are typically formed from the reaction of an acid and a base, such as sodium chloride (NaCl), which is formed from hydrochloric acid and sodium hydroxide.
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