Class 10th CH-2 Notes Acid Bases Salts

Class 10th CH-2 Notes Acid Bases & Salts
Class 10th CH-2 Notes Acid Bases & Salts

Q. What do you mean by Acids?

Generally, the term ‘Acid’ has been derived from the Latin word, ‘Acidus’ which means sour in taste. The Substances which are Sour in taste is known as Acids. Ex: Lemon, Vinegar, etc.

Q. What are some Characteristics of Acids:

  1. Acids are sour in taste.
  2. They turn the Blue Color of litmus paper into red color.
  3. Release H+ ions in aqueous solution.
  4. Acids react with Metal to produce H2(hydrogen) gas.
  5. They do not corrode to the Metals.

Some Examples of Strong acids;- HCl, H2SO4, HNO3, etc…

Some Examples of Weak Acids:- CH3COOH, Oxalic Acid, Lactic Acid, etc…

Concentrated acid:– Any Solution which, Having more amount of acid + less amount of water, is known as Concentrated Acid.

Dilute Acid:- Any Solution which, Having more amount of water + less amount of acid, is known as Dilute Acid.

Q. What do you mean by Bases?

Generally, The Substances which are Bitter in Taste and Soapy to touch are known as bases. Ex: Sodium hydroxide (NaOH).

What are some Characteristics of Bases:-

  1. Substances that are bitter in taste and soapy in touch.
  2. These turn Red color Litmus paper into Blue color.
  3. Bases releases OH- ion in the Aqueous Solution.
  4. Bases don’t shows any reaction with the Metals.
  5. They corrode the Metals.

Some Examples of Strong Bases are:- NaOH, KOH, Ca(OH)2,

Some Examples of weak Bases are:- NH4OH (Ammonium hydroxide).

Q. What do you mean by the term ‘Alkalis’?

The Bases which are highly soluble in water are known as Alkalis.


The substances which are formed by the reaction of Acids and Bases are known as Salt. Acid + Base —-> Salt + water

Example:- NaCl (Sodium chloride), KCl (Potassium Chloride).

What are the Indicators:-

These are the Substances that change their color/smell according to the Acid or Base.

Types of Indicators:-

  1. Natural Indicator.
  2. Synthetic Indicator (man-made).
  3. Olfactory (sense of smell) Indicator.

What are Natural Indicators:-

The indicators which are found in the natural plants or Extracted from the natural products are known as Natural Indicators. Ex:- Litmus, Red cabbage, flowers of hydrangea plant, Turmeric.

Synthetic Indicators:- These are also known as man-made Indicators. These are made form the Chemical Substances. Example:- methyl orange, Phenolphthalein.

Olfactory indicators:- The Substances that change their smell (odor) in the presence of an acid or base are known as olfactory indicators. Example:- Vanilla essence, Onion, Clove Oil.

Some Chemical Properties of Acid Bases & Salts.

Q. How do acids react with metals?

Ans:- When acids react with the Metals then H2 (hydrogen gas) is released. As well as the Reaction that takes place is Displacement Reaction.

Eg:- 2HCl + Zn —> ZnCl2 + H2

Q. How do bases reacts with the Metals?

Ans:- Similarly, when Bases reacts with the Metals they also produce Metal Salt and H2 (Hydrogen gas)

Acid + Metal —-> Metal Salt + H2 (hydrogen gas)

Bases + Metal —-> Metal Salt + H2 gas.

—–>**Hydrogen gas released can be checked by bringing the Burning candle near the gas. Or when you pass the hydrogen gas through the Soap water then the Bubbles will burst with the pop sound.

Q. How do Metal Carbonates and Metal Hydrogen Carbonate react with Acid and Bases?

Acid + Metal Carbonate/ Metal hydrogen Carbonate ——> Salt + CO2 + H2O.

Base + Metal Carbonate/Metal Hydrogen Carbonate ——-> No Reaction.

Example:- 2HCl + Na2CO3 —–> 2NaCl + CO2 + H2O

HCl + NaHCO3 ——-> NaCl + CO2 +H2O

**CO2 can be tested by passing it through lime water.

Ca(OH)2 + CO2 —–> CaCO3 + H2O (Lime water turns Milky.)

**When excess CO2 is passed,

CaCO3 + CO2 + H2O ——> Ca(HCO)3 (Milkiness Disappears.)

What happened when Acids and Bases React Together.

Acid + Base ——> Salt + H2O (water)

What is Neutralization Reaction: This is a type of reaction in which, acid and bases react together to form Salt and water.

Eample: HCl + NaOH ——> NaCl(sodium choloride) + H2O (water)

Q. What will happened if acids will react in Different Form:-

Strong Acid + Weak base —–> Acidic Salt + H2O

Weak Acid + strong Base ——-> Basic Salt + H2O

Q. Reaction of Metallic oxides with Acids:-

Ans:- Metallic Oxides are generally, Basic in nature. Example:- CaO, MgO are basic oxides. Metallic Oxide + Acid ——> Salt(Basic in nature) +H2O

CaO + 2HCl —-> CaCl2 + H2O

Reaction of Non-Metallic oxides with Bases:

Non-Metallic oxides are Generally, Acidic in Nature. Non-Metallic oxide + Base —-> Salt (acidic in nature) + H2O

CO2 + Ca(OH)2 —–> CaCO3 + H2O

***What will happen when Acid reacts with,

  1. Acid + Metal carbonate ——> Salt + CO2 + water.
  2. Acid + Metal —–> Salt + H2
  3. Acid + Metal Hydrogen Carbonate —–> Salt + CO2 + H2O
  4. Acid + Metallic Oxide —–> Salt + H2O
  5. Acid + Base ——> Salt + water

***What will happens when Base reacts with,

  1. Base + Metal —-> Salt + H2
  2. Base + Metal Carbonate ——> No Reaction
  3. Base + Metal Hydrogen carbonate —–> No reaction
  4. Base + metallic oxide ——> Salt = H2O
  5. Base + Acid ——-> Salt + H2O (water)

What do all Acids and Bases have in Common:

  1. All acids have H+ ions in common.
  2. Acids produce H+ ions in solution, which are responsible for their Acidic Properties.
  3. All Bases have OH- (Hydroxyl ions) in common.

**Acid or Base in Water solution

Acids produce H+ ions in the presence of water.

H+ ions cannot exist alone, they exist as H3O+ (hydronium ions).

H+ + H2O ——> H3O+

HCl + H2O ——> H3O+ + Cl-

When bases dissolved in water gives OH- ions.

NaOH ——–> Na+ OH-

Mg(OH)2 ——–> Mg2+ 2OH-

  • Bases Soluble in water is called Alkali.

Note:- While Diluting Acids, It is Recommended that the Acid Should be added to water not water to Acid. Because the Process of dissolving an Acid and base in water is highly Exothermic.

If water is added to the acid, the heat generated may cause the mixture to splash out the cause burns and the glass container may also break due to excessive local Heating.

Q. What will happen if you add acid to water?

  1. Cause mixture to splash out Because the reaction is very Exothermic.
  2. Break the glass Container.

Q. What is Dilution?

Ans:- Missing an Acid or a base with H2O results in the decrease of concentration of ions (H3O+/OH-) per unit Volume. Such a process is called Dilution.

Q. How can we Estimate the Strength of Acid and Base

Ans:- Strength of Acid or Base can be estimated using a universal Indicator.

Q. What is the Universal Indicator?

Ans:- It is a Mixture of Several Indicators. It shows different colors at different concentration of H+ ions in the Solution.

pH Scale:-

**This is a type of Scale, which helps in measuring H+ ion concentration in the solution. P in the PH represents to the Power and H represents Hydrogen.

pH = 7 —-> Neutral Solution.

When pH less than 7 —> Acidic Solution.

pH more than 7 ——> Basic Solution.

*** On Dilution an Acid: pH increases

On diluting a Base: pH decreases.

Importance of pH in everyday life.

pH of Salts;-

(i). Strong Acid + Strong base —–> Neutral Salt : pH = 7

(ii). Salt of Strong acid + weak base ——> Acidic salt: < 7

(iii). Salt of Strong base + Weak Acid ——> Basic Salt > 7

  1. Sodium Hydroxide (NaOH):-

When Electricity passes through an aqueous solution of NaCl (also known as Brine), then it decomposes to form NaOH (Sodium Hydroxide). This is also known as (Chlor-Alkali Process).

2NaCl(sodium choloride) + 2H2O —> 2NaOH(sodium hydroxide) + Cl2 + H2

At Anode —-> Cl2 gas will release.

At Cathode —-> H2 gas will release.

Near Cathode: —-> NaOH solution is Formed.


H2: In Fuels, Margarine.

Cl2: In Water Treatment, PVC, CFC’s.

HCl: In Cleaning Steels, Medicines.

NaOH: In Degreasing Metals, Soaps and Papermaking.

Cl2 + NaOH——> Bleach (NaClO): Household bleaches, Bleaching Fabrics.

2. Bleaching Powder (CaOCl2):

It is produced by the action of chlorine on dry slaked lime.

Cl2 + Ca(OH)2 —–> CaOCl2(calcium oxychloride) + H2O


(a). Bleaching cotton and Linen in the textile Industry.

(b). Bleaching wood pulp in paper Factories.

(c). The oxidizing agent in a chemical Industries.

(d). Disinfecting drinking water.

3. Baking Soda (Sodium hydrogen carbonate) (NaHCO3)

NaCl + H2O + CO2 + NH3 ——> NH4Cl + NaHCO3 (Sodium Hydrogen Carbonate).

  • It is a Mild non-Corrosive base.
  • When it is heated during cooking.

2NaHCO3 ——> Na2CO3 + H2O + CO2


  • Making Baking powder (Mixture of Baking soda and tartaric acid). When baking powder is heated or mixed with water, CO2 is Produced which causes bread and cake to rise to make them soft and Spongy.
  • An Ingredient in Antacid.
  • Used in Soda acids, fire extinguishers.

Washing Soda (Na2CO3.10H2O):

Recrystallization of sodium carbonate gives washing soda. It is a basic Salt.

Na2CO# = 10H2O —-> Na2CO3.10H2O


(a). In Glass, Soap and Paper Industry.

(b). Manufacture of Borax.

(c). Cleaning agent for domestic purposes.

(d). For removing the permanent hardness of the water.

Plaster of Paris (Calcium Sulphate HemiHydrates) (CaSO4.1/2 H2O)

On heating Gypsum (CaSO4.2H2O) at 373k, It loses water molecules and becomes plaster of Paris (POP).

It a white powder and on mixing with water it changes to gypsum.

CaSO4.1/2H2O + 1.5 H2O ——–> CaSO4.2H2O


(a). Doctors use POP for supporting fractured bones.

(b). For making toys, Materials for Decorations.

(c). For making Surface smooth.

The water of Crystallization:- It is a fixed number of water molecules present in one formula unit of salt.

Example:- CuSo4.5H2O has 5 water Molecules.

Na2CO3.10H2O has 10 water Molecules.

CaSO4.2H2O has 2 Water Molecules.

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