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Science Class 10 - Bases And-Salts Notes

Comprehensive study notes for Class 10 - Bases And-Salts olympiad preparation

Bases and Salts

Welcome to the chapter on Bases and Salts for Class 10. In this chapter, you will learn what bases and salts are, their properties, how they are formed, and their uses in daily life. By the end of this chapter, you will be able to identify bases and salts, write their chemical reactions, and understand their importance in chemistry and everyday life.

Introduction

Bases and salts are important classes of chemical compounds. Bases are substances that can accept hydrogen ions (protons) or donate a pair of valence electrons. Salts are formed when acids react with bases or metals.

What are Bases?

  • Base: A substance that tastes bitter, feels soapy, and turns red litmus paper blue.
  • Bases release hydroxide ions (OH-) in water.
  • Examples: Sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2).

Properties of Bases

  • Bitter taste and slippery feel.
  • Turn red litmus paper blue.
  • React with acids to form salt and water (neutralization reaction).
  • Conduct electricity in aqueous solution.

What are Salts?

  • Salt: A compound formed when the hydrogen ion (H+) of an acid is replaced by a metal ion or ammonium ion.
  • Salts are usually formed by the reaction of an acid with a base, metal, or carbonate.
  • Examples: Sodium chloride (NaCl), potassium nitrate (KNO3), calcium sulfate (CaSO4).

Formation of Salts

  • Acid + Base → Salt + Water (Neutralization reaction)
  • Acid + Metal → Salt + Hydrogen gas
  • Acid + Carbonate → Salt + Water + Carbon dioxide

Example: HCl + NaOH → NaCl + H2O

Types of Salts

  • Normal Salts: Formed by complete replacement of hydrogen ions of an acid by a metal.
  • Acid Salts: Formed by partial replacement of hydrogen ions.
  • Basic Salts: Formed by partial replacement of hydroxide ions of a base.

Uses of Bases and Salts

  • Sodium hydroxide is used in making soap and paper.
  • Calcium hydroxide is used in whitewashing.
  • Sodium chloride (common salt) is used in food.
  • Salts are used in fertilizers, medicines, and industry.

Fun Activity: Test with Litmus Paper

Take a small amount of soap solution and dip red litmus paper in it. What happens? Try the same with salt water. Observe the changes!

Summary

  • Bases are bitter, soapy, and turn red litmus blue.
  • Salts are formed by the reaction of acids with bases, metals, or carbonates.
  • Both bases and salts are useful in daily life and industry.

Practice Questions

  1. What is a base? Give two examples.
  2. How is a salt formed?
  3. Write the reaction between hydrochloric acid and sodium hydroxide.
  4. Name two uses of sodium chloride.
  5. What happens when an acid reacts with a carbonate?

Challenge Yourself

  • Classify the following as acid, base, or salt: NaOH, H2SO4, NaCl, Ca(OH)2, KNO3.
  • Explain why common salt is important for our body.

Did You Know?

  • Baking soda (sodium bicarbonate) is a salt used in cooking and cleaning.
  • Some salts can be colored, like copper sulfate (blue) and potassium permanganate (purple).

Glossary

  • Base: A substance that releases hydroxide ions in water.
  • Salt: A compound formed from the reaction of an acid and a base.
  • Neutralization: A reaction between an acid and a base to form salt and water.
  • Litmus Paper: A paper strip used to test acids and bases.

Answers to Practice Questions

  1. A base is a substance that releases hydroxide ions in water. Examples: NaOH, KOH.
  2. A salt is formed when an acid reacts with a base, metal, or carbonate.
  3. HCl + NaOH → NaCl + H2O
  4. Used in food and as a preservative.
  5. Salt, water, and carbon dioxide are formed.

Explore the world of chemistry by observing bases and salts around you!

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