Acids Bases and Salts Notes

The short notes for the chapter Acids Bases and Salts are as follows:

Acids

Acids are the one which:

1. Produce [H⁺] in H₂O
2. Has sour taste
3. Turns blue litmus red
4. Acts as electrolyte in solution

Chemical Properties Of Acids

• Acids + Metal → Salt + H₂
  e.g., H₂SO₄ + Zn → ZnSO₄ + H₂
• Acids + Metal Carbonate/Metal hydrogen
  Carbonate = Salt + CO₂
  e.g., NaHCO₃ + HCl → NaCl + H₂O + CO₂
• Acids + Bases → Salt + water
  e.g., NaOH + HCl → NaCl + H₂O
• Acids + Metal oxide → Salt + Water
  e.g., H₂SO₄ + CuO → CuSO₄ + H₂O

Bases

Bases are the one which:

1. Produce [OH^–] in H₂O
2. Has bitter taste
3. Turns red litmus blue
4. Acts as electrolyte in solution
5. Water soluble bases are known as alkali

Chemical Properties Of Bases

• Bases + Metals → Salt + H₂
  e.g., 2NaOH + Zn → Na₂ZnO₂ + H₂
• Bases + Acids → Salt + Water
  e.g., KOH + HCl → KCl + H₂0
• Base + Non-metallic oxide → Salt + water
  e.g., 2NaOH + CO₂ → Na₂CO₃ + H₂O

Salts

Salt is formed by combination of acid and base through neutralization reaction, e.g. reaction of HCl with NaOH produce NaCl which is a salt.

NaCl is called as common salt or table salt used in households.

Water of Crystallization

It is the fixed number of water molecules present in one formula unit of a salt, e.g.CuSO₄.5H₂O, Na₂CO₃.10H₂O.

Types of Salts

The acidic and basic nature of salts depends on the acid and base combined in neutralization reaction, which is mentioned in the table given below:

pH	Acid	Base	Salt	Example
7	Strong	Strong	Neutral	NaOH + H2SO4 → Na2SO4 + H2O
< 7	Strong	Weak	Acidic	HCl + NH4OH → 4 NH4Cl + H2O
> 7	Weak	Strong	Basic	CH3COOH + KOH → 4 CH3COOK + H2O
	Weak	Weak	Weak	CH3COOH + NH4OH → CH3COONH4 + H2O

Important Salts

(a) Plaster of Paris (CaSO₄.¹/₂H₂O):

Used for making toys, material for decoration, smooth surfaces.

(b) Bleaching Powder (CaOCl₂):

Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O

Used as an oxidising agent in chemical industry, in disinfecting water.

(c) Common Salt (NaCl): Main source is sea water, also exists in the form of rock hence also known as rock salt. It is an important component of food.

Used in preparation of sodium hydroxide, baking soda & washing soda.

(d) Baking Soda (NaHCO₃):

NaCl + H₂O + CO₂ + NH₂₃ → NH₄Cl + NaHCO₃

Mild non – corrosive

Used as in baking cakes as antacid, in fire extinguisher.

(e) Sodium Hydroxide (NaOH):

Prepared by chlor-alkali process.

(f) Washing Soda (Na₂CO₃. 10H₂O) :

Na₂CO₃ + 10H₂O → 4 Na₂CO₃. 10H₂O

Used in glass, soap & paper industry, removing Permanent hardness of water and cleaning agent

Indicators

These are the substances which indicate the acidic or basic nature of the solution by their colour change.

Indicators	Colour in Acidic medium	Colour in Basic medium
Litmus solution	Red	Blue
Methyl orange	Pink	Orange
Phenolphthalein	Colourless	Pink
Methyl red	Yellow	Red

Strength of Acids and Bases in Solution

• Some animals like bee and plants like nettle secretes highly acidic substance for self defense.
• Lower pH of sour & sweet food can cause tooth decay. The pH of mouth should be more than 5.5
• The inner lining of stomach protects vital cells from the acidic pH which is developed by HCl secreted by stomach.
  The optimum pH range for human body is 7 to 7.8

pH = 7	Neutral Solution	[H3O+]=[OH–]
pH > 7	Basic Solution	[OH–]>[H3O+]
pH < 7	Acidic Solution	[OH–]<[H3O+]

Addition of Acids or Bases to Water

Always add acid to water and not water to acid because this process is highly exothermic. The acid must be added slowly to water by constant shirring on. Adding water to a concentrated acid, the heat generated may cause the mixture to splash out and cause burns.

Read More: Chemical Reactions and Equations Notes

Follow here: https://www.facebook.com/cgschemistrysolutionss

• YouTube