Acids , Bases and salts

Introduction;

Acids: The word ‘Acid’ came from Latin word ‘Acidus or Acere’ which means sour.

            Sour taste is the most common characteristic of acid.

             Acid turns blue litmus paper red.

             There are many substances which contain acid and hence taste sour, such as curd,    oranges, lemon, etc.

            Hydrochloric acid present in stomach and help in digestion.

            Acids may be Natural and mineral.

            Natural acids:

            Acids which are obtained from natural sources are called natural acid or organic acid.

           

Organic Acids & Source
Acid	Source
Acetic acid	Vinegar
Ascorbic acid	Guava, amla
Citric acid	Lemon, orange and other citrus fruits
Lactic acid	Sour milk, curd
Methanoic acid	Ant sting, nettle sting
Oxalic acid	Tomato
Tartaric acid	Tamarind

           

Mineral Acids: Acids that prepare from mineral are known as mineral acids, inorganic acids, man-made acids or synthetic acid, such as hydrochloric acid, sulphuric acid, nitric acid, etc.

Base: Base is bitter in taste and feels soapy on touch.                                                                           A base turns red litmus paper blue.

Sodium hydroxide (caustic soda), calcium hydroxide, sodium carbonate (washing soda), lime (Calcium oxide), potassium hydroxide (caustic potash), etc. are examples of base.

Salt                                                                                                                                                                   Salts are the ionic compounds which are produced after the neutralization reaction between acid and base. Salts are electrically neutral. There are number of salts but sodium chloride is the most common among them. Sodium chloride is also known as table salt or common salt. Sodium chloride is used to enhance the taste of food.

Explain arhenius and lowry- Bronsted concepts about acids and bases

1; Arhenius concept; according to him acids are those substances which can produce H⁺ ions ,   

            when dissolve in water

            HCl + H₂O → H⁺ + Cl^-

            acid

            HNO₃ + H₂O → H⁺ + NO₃^-1

            acid

            HCl and HNO₃ are acids because they give H⁺ ions when dissolve in water

            Similarly bases are those substances which give OH^- ions when dissolve in water.

            NaOH + H₂O → Na⁺ + OH^-

            Base

            Ca(OH)₂ + H₂O → Ca⁺² + 2OH^-1

            NaOH and Ca(OH)₂ are bases as they give OH^- ions in aqueous solutions.

            According to Arhenius water is neutral and is just medium for the ionization of acid or base.

            Other acids according to Arhenius are , H₂SO₄ , H₃PO₄,  HBr  e.t.c

            Other bases according to Arhenius are KOH , RbOH , Ba(OH)₂

LOWRY BRONSTED ACID AND BASE;

            Johanas Bronsted and Martin lowry present a new concept about acid and base.

            1; Acid;( Proton Donor)

          Those species which donate the proton or have the tendency to donate proton are called acids.

            2; Base; (Proton Acceptor)

            Those species which accept the proton or have the tendency to accept proton are bases.

            Example;                     HCl  +  H₂O      H₃O⁺  +           Cl^-

                                      Acid        Base      

                In this example H₂O act as base because it accept proton while HCl donate proton and is acid.

                                        

                According to Lowry and bronsted H₂O may be acid or base because it has the tendency to accept            as well as donate proton.

            NH₃ + H₂O    NH₄⁺                  +          OH^-

            ^{base          Acid}         

                here H₂O is acid because  it donate proton while NH₃ is base.               

               

                NH₃ + HCl            NH₄⁺           +                Cl^-   

            Base    acid