Class 10 Science Chapter 2 Notes

Prepare Class 10 Science Chapter 2 using simplified Notes with keywords and explanation. All the definition and equations related to 10th Science Chapter 2 Acids, Bases and Salts are given below. Student of UP Board and MP Board also take the benefits of these notes, as they are using NCERT for the new academic session 2024-25.

Sources of Natural Acids

• Citric acid: Found in lemon, orange, and in most of the citrus fruits.
• Acetic acid (Ethanoic acid): Found in vinegar.
• Tartaric acid: Found in Tamarind
• Oxalic acid: Found in tomato
• Lactic acid: Found in sour milk, curd, etc.
• Formic acid: Found in ant sting, nettle sting
• Ascorbic acid: Found in guava, amla, etc.

Dilution of Acids

Acid can be diluted by mixing of acid into water. Dilution of acid is an exothermic process.
Caution: Always acid is slowly mixed in water to dilute the acid. Never mix water into acid to dilute. Mixing of water into acid can be very dangerous.

Bases

A base gives bitter taste. A base feels soapy when touched. A base turns red litmus paper blue.
Example: Caustic soda (sodium hydroxide), washing soda (sodium carbonate), potassium hydroxide, slaked line (calcium hydroxide), etc. All metal oxides, metal hydroxides, metal carbonates are base.
Chemical properties of base are just opposite to that of acids. When a base is added to acid, both neutralize each other, in such reactions respective salts are formed along with water Oxides, hydroxides, and carbonates of all metals are base.

Example:
Calcium is an alkaline earth metal, thus its oxide, calcium oxide (quick lime), its hydroxide, which is known as calcium hydroxide (slaked lime) and its carbonate calcium carbonate (lime stone) are base.
Sodium is an alkali metal, thus sodium oxide, and sodium hydroxide and sodium carbonate are base.
Potassium is an alkali metal thus potassium oxide, potassium hydroxide and potassium carbonate are base.

Types of base

On the basis of solubility in water, bases are divided into following two types:

• (a) Water soluble base – Alkalis.
• (b) Water insoluble base – Base.
  Most of the bases are insoluble in water. Bases which are soluble in water called alkalis.

Do you know, what is an alkali?

Water soluble base is known as alkalis.
Alkali is a basic ionic salt of alkaline metals. Lithium, sodium, potassium, etc. are called alkali metals. Beryllium, magnesium, calcium etc. are called alkaline earth metals. Therefore hydroxides of alkali and alkaline earth metals are called alkalis.
Example: sodium hydroxide, calcium hydroxide, potassium hydroxide, lithium hydroxide, etc.
Ammonium hydroxide is another important base, although it is the hydroxide of non-metal.
Ammonia is a hydride (salt) of non – metal, but it is a base.
Most of the reactions takes place in aqueous state, thus water soluble base are more useful.

Properties of acids

1. Acids are sour in taste.
2. All acids give H+ hydrogen ion with water.
3. It turns colour of blue litmus to red.
4. Acids conduct electricity current.
5. It reacts with metals produces salt and hydrogen gas.

Properties of Bases

• Bases are bitter in taste.
• All bases give (OH–) hydroxide ion with water.
• It turns colour of red litmus into blue.
• Bases conduct electricity current.
• It also reacts with metals gives salt and hydrogen gas.

Historical Monuments and Acid Rain

Burning of fossil fuels releases oxides of sulphur and nitrogen. Nitrogen oxide and sulphur dioxide form nitric acid and sulphuric acid on reaction with water. When rain droplets mix with these gases; present in atmosphere because of pollution; they form acid rain.
Acid rain causes damage to the historical monuments and other buildings. For example Taj Mahal, which is made of marble, is getting damaged because of reaction with acid rain. Marble is calcium carbonate which reacts with the acid and thus gets corroded.

pH Scale

The concentration of hydrogen ion in a solution can be determined using pH scale. In the word pH, p stands for potency or power and H stands for Hydrogen ions. p came from German word ‘potenz’ which means power. In totality it can be said that pH means power of an acid.

• pH scale is a tool using which hydrogen ion concentration is measured.
• pH scale works on the value from 0 to 14 (zero to fourteen).
• 0 (zero) value on pH scale indicates highly acidic (strongest acid)
• 7 (seven) value on pH scale indicates the neutral solution
• 14 (fourteen) value on pH scale indicates highly basic (strongest base)
• Strength of acid, i.e. acidity increases with decreasing of value on pH scale from 7 (seven) to (0) zero
• Strength of base, i.e. basicity increases with increasing of value on pH scale from 7 (seven) to 14 (fourteen)
• Thus, by knowing the value of on pH scale strength of an acid or a base can be determined.

Chlor-Alkali Process:

When electricity is passed through an aqueous solution of sodium chloride (called brine), it decomposes to form sodium hydroxide. The process is called the chlor-alkali process.
This process is taken place by electrolysis of aqueous sodium chloride.

The chemical equation of this process is as folllow:
2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2 (g) + H2(g)

When electricity is passed through an aqueous solution of sodium chloride (called brine), Chlorine gas is given off at the anode, and hydrogen gas at the cathode. Sodium hydroxide solution is formed near the cathode.

Products of chlor-alkali Process:

• (1) Sodium Hydroxide
• (2) Chlorine Gas
• (3) Hydrogen Gas

Uses of Sodium Hydroxide

• (i) It is used for de-greasing Metals.
• (ii) In soaps and detergents.
• (iii) In Paper making.
• (iv) For making of artificial fibres.

Uses of hydrogen

Production of Hydrochloric acid: Chlorine and Hydrogen are the main products of chlor-alkali process. These are used for production of Hydrochloric acids. Hydrochloric acid is important chemical product which is used in manufacturing of medicines, cosmetics and ammonium chloride and also used for cleaning steel.

• (i) It is used as fuels.
• (ii) It is used in Margarine.
• (iii) In manufacturing of ammonia for fertilisers.

Uses of Chlorine gas

1. It is used In water treatment.
2. In swimming pool.
3. In manufacturing of PVC, CFCs and pesticides.
4. It is also used as disinfectants.