10 Class- Acids, Bases and Salts

Acids Bases and Salts

·       Natural indicator of acids and bases – Litmus, Turmeric
·       Synthetic indicator of acids and bases – Methyl Orange, Phenolphthalein
·       Olfactory indicators of acids and bases – Odor of these substance changes in acids and bases.

pH scale for acid neutral and alkaline (or base) - Acid base strength indication by H and OH ion concentration
pH scale for Acid Neutral and Alkaline (or Base) & Acid Base strength indication by H and OH ion concentration

What is Acid?

Acids are the chemicals which can donate a proton or accept an electron pair in chemical reactions having pH less than 7 and changes color of blue Litmus to red.
Example- HCl, H2SO4

What is Base?

Bases are the chemicals which can accept a proton or donate an electron pair in chemical reactions having pH more than 7 and changes color of red Litmus to blue.
Bases which dissolve in water are called as Alkali
Example- NaOH

What is Salt?

Example- NaCl

Acids and Bases Reaction with Metals:-

                   Metal react with acid to form salt.
Acid + Metal ——> Salt + Hydrogen Gas
Metal react with base to form salt.
Base + Metal ——> Salt + Hydrogen Gas

Reaction of Metal Carbonates and Metal Hydrogen-Carbonates with Acids:-

Metal carbonates and metal hydrogen carbonates react with acids to form salt, water and carbon dioxide.
Metal Carbonate + Acid —–> Salt + Water + Carbon Dioxide
Example- Na2CO3+ 2HCl –—-> 2NaCl + H2O + CO2
Metal Hydrogen Carbonate + Acid —à Salt + Water + Carbon Dioxide
Example- NaHCO3 + HCl –—-> NaCl + H2O + CO2

Reaction of Acids with Bases:-

Reaction of acids with bases to form salt and water is called neutralization reaction.
Acid + Base —–> Salt + Water

Reaction of Acids with Metallic Oxides:-

Acids react with Metallic Oxides to form salt and water.
Acid + Metallic Oxide —–> Salt + Water

Reaction of Bases with Non-Metallic Oxides:-

Non-Metallic Oxides are acidic in nature so these react with bases to form salt and water.
Base + Non-Metallic Oxide —–> Salt + Water

Acids or Bases in Water:-

When acids dissolve in water they produce Hydrogen Ion H+(Aq) or Hydronium Ion (H3O+)
HCl + H2O —> H3O+ + Cl
H+ + H2O —> H3O+
When bases dissolve in water they produce Hydroxide Ions (OH)
NaOH + H2O ——> Na+(Aq) + OH(Aq)
Reactions of Acids or Bases with Water are highly exothermic. Process of mixing Acid or Base with water decrease concentration of ions per unit volume, this process is known as dilution. 

Strength of Acids or Bases:-

Strength of acids depends on number of hydrogen ions (H+) produced and strength of bases depends on number of hydroxide ions (OH) produced. A universal indicator (present on pH paper) is used to find strength of acids or bases.

pH Scale:-

It is a scale to measure hydrogen ion concentration in solution.
Meaning of ‘p’ in ‘pH’ is “potenz”, which is a German word whose meaning is “power”.
pH scale measure pH from 0 (very acidic) to 14 (very alkaline).
pH of Neutral Solution is 7
pH of Acidic Solution is less than 7
pH of Basic Solution is more than 7

 What is acid rain?

If pH of rain water is below 5.6 on pH scale than, that rain is called as acid rain.

Some Naturally Occurring Acids:-

Natural Source
Acetic Acid
Citric Acid
Tartaric Acid
Oxalic Acid
Sour Milk (Curd)
Lactic Acid
Citric Acid
Ant Sting
Methanoic Acid
Nettle Sting
Methanoic Acid

Common Salt:-

Common salt is very important raw material for production of other daily use material.

Sodium Hydroxide:-

Sodium Hydroxide is obtained by passing electricity through aqueous solution of sodium chloride (brine). Process is known as Chlor-Alkanization.   
2NaCl (aq) + 2H2O (l) —-> 2NaOH (aq) + Cl2(g) + H2 (g)

Bleaching Powder (CaOCl2):-

Bleaching Powder is obtained by reaction between chlorine (Cl2) and dry slaked lime [Ca(OH)2].
Ca(OH)2 + Cl2—–> CaOCl2 + H2O

Use of Bleaching Powder:-

·       For bleaching wood pulp in paper industry.
·       For bleaching washed clothes in laundry.
·       For bleaching cotton and linen in textile industry.
·       Used as oxidizing agent in chemical industry.
·       Used as disinfectant for drinking water to kill germs.

Baking Soda:-

Chemical name of baking soda is sodium hydrogen carbonate (NaHCO3). It is obtained by reaction between Sodium Chloride (NaCl), Water (H2O), Carbon Dioxide (CO2) and Ammonia (NH3).
NaCl + H2O + CO2 + NH3 —-> NH4Cl (Ammonium Chloride) + NaHCO3 (Sodium Hydrogen Carbonate)

Uses of Sodium Hydrogen Carbonate:-

·       To produce baking powder {mixture of baking soda + mild edible acid (like tartaric acid)}
·       Used to produce antacids (neutralize access acid in stomach to provide relief from acidity)
·       Used in soda acid fire extinguishers

Washing Soda:-

Washing soda is obtained by heating baking salt (Sodium Hydrogen Carbonate) and recrystallization of Sodium Carbonate produced above.
2NaHCO3 (Sodium Hydrogen Carbonate) + Heat ——–> Na2CO3 (Sodium Carbonate) + H2O + CO2
Na2CO3+ 10H2O ——–> Na2CO3.10H2O

Uses of Washing Soda:-

·       Used in glass, soap and paper industries
·       Used in preparation of sodium compounds like borax
·       Used as cleaning agent
·       Used for removal of permanent hardness of water

Crystal of Salt:-

Presence of fixed no. of water molecules in one formula unit of salt is called as water of crystallization.
·       Copper sulphate crystals with water molecule (CuSO4.5H2O) are blue in color, while
·        Copper sulphate crystals without water molecule (CuSO4) are white in color.

Plaster of Paris:-

Plaster of Paris is obtained by heating gypsum (CaSO4.2H2O) at 373K.
CaSO4.2H2O (Gypsum) + Heat —-> CaSO4.1/2H2O (Plaster of Paris) + 3/2H2O

Uses of Plaster of Paris:-

·       Used by orthopedic doctors for supporting fractured bones.

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