Class 10 - Chemistry Ch 2...... Acid, Bases and Salts Notes

ACIDS, BASES AND SALTS

Acids

·         Acids is defined as the one which produces hydrogen ions in water. For Example, Sulphuric Acid, Hydrochloric Acid etc.

·         They give sour taste.

·         Acids turn blue litmus to red. This is used as confirmation test for the presence of acid.

·         When acids react with metals, gases are evolved.

Reactions with Acids

1. Reaction of Acid with Metal

Acid + Metal → Salt + Hydrogen gas

Mg + H₂ SO₄ → H₂ + Mg SO₄

2. Reaction of Acid with Carbonates

Na₂ CO₃ (s) + 2 HCl (aq) → 2NaCl (aq) + H₂O(l) + CO₂(g)

3. Reaction of Acid with Bicarbonates

NaHCO₃ (s) + HCl (aq) → NaCl(aq) + H₂O (l) + CO₂ (g)

Similarity between Acids and Bases

·         Both acids and base react with water. They produce ions in water

·         Both acids and bases acts as electrolytes, so are good conductors of electricity.

·         Both of them changes the colour of the litmus paper.

Classification of Acids

Acids are classified as Organic Acids and Mineral Acids. Acids which are derived from plants and animals, they are known as Organic Acids. For Example, Citric Acid from fruit. Mineral acids are inorganic acids such as Sulphuric Acid. They are dangerous to be used, so need more precautions.

Acids are also classified as Strong Acids or Weak Acids. Strong acid is an acid, that completely dissociates into ions in aqueous solutions. For Example, Sulphuric Acid, Hydrochloric Acid.

Weak acid is the one which does not dissociate completely into ions in aqueous solutions. For Example, Acetic Acid.

Acids can also be as Dilute Acid and Concentrated Acids. The one which has low concentration of acids in aqueous solution, they are known as Dilute Acids whereas the one which has high concentration of acids in aqueous solution, are known as Concentrated Acids.

It is advisable to add acid to water and not vice versa because large amount of heat is released if water is added to acid. This released heat is large enough to cause harm.

Acids can also be classified based on number of hydrogen ions. Monoprotic acid is the one which gives one mole of hydrogen ions per mole of acid, such as HCl. Diprotic Acid is the one which produces two mole of hydrogen ions per mole of acid. For Example, H₂SO₄.

Bases

·         Bases are the one which produces hydroxide ions in aqueous solutions. Bases which are water soluble they are known as Alkalis.

·         They turn red litmus to blue.

·         They have a bitter taste.

·         They also produced carbon-dioxide when reacted with carbonates.

·         They also evolved hydrogen gas when bases react with metals.

Reactions of Bases

1. Reaction with Metals

Base reacts with metals and produce hydrogen gas.

2NaOH + Zn → Na₂ → Na₂ZnO₂ + H₂

2. Reaction with Acids

Base reacts with acids to form salts. For Example,

KOH + HCl → KCl + H₂O

3. Reaction with Non-metallic Oxides

Base reacts with non-metallic oxides to form salt and water.

2NaOH + CO₂ → CO_2­ → Na₂CO₃ + H₂O

Classification of Bases

Bases are classified as Strong Base and Weak Base. Strong base is the one which dissociates completely into its ions in aqueous solution. For Example, NaOH.

Weak base is the one which does not dissociate completely into its ions in aqueous solutions. For Example, Ammonium Hydroxide, NH₄OH

Bases are also classified as Dilute Base and Concentrated Base. The solution which has low concentration of base in aqueous solution is defined as Dilute Base whereas the one which has high concentration of base in aqueous solution is known as Concentrated Base.

 

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