·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
What is Acid?
Acids are the chemicals which candonate 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 canaccept 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
What is Salt?
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.
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:-
Sour Milk (Curd)
Common salt is very important raw material for production of other daily use material.
Sodium Hydroxide is obtained by passing electricity through aqueous solution of sodium chloride (brine). Process is known as Chlor-Alkanization.