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1. Definition of Acid and Bases: 1.1 Arrhenius definition of acid and base: Arrhenius Acid: The substance or a compound which gives H+ ions in aqueous solution Arrhenius base: Base is a substance or compound that produces OH- ions in aqueous solutions. Chemists have known for some time that the H+ ion doesn’t exist in aqueous solutions as an independent species. The modernized Arrhenius definition of acid is that they are substances that produce H3O+ ions in aqueous solutions. It did not take longer for chemist to find other problems with the Arrhenius definition. In practical terms, the OH- ion is far from being the only base. 1.2 Bronsted-Lowry definition: Bronsted-Lowery definitions acid and a base, consider the net ionic equation for any Arrhenius acid-base reaction in water: H3O+ + OH- 2H2O When it reacts, the H3O+ ion gives up a proton, passing it to the OH- ion. This means that H3O+ is a Bronsted-Lowry acid in this reaction. The OH- in turn accepts the proton, making it a Bronsted-Lowry base. The advantages of the Bronsted-Lowry definitions are that they cover acids and bases other than H3O+ and OH- .Consider: HSO4- + PO43- SO4- + HPO42- During this reaction the HSO4- ion donates a proton and is therefore an acid. The reaction ion turns the HSO4- ion into the SO4- ion. The PO43- ion becomes the HPO4- ion during the same reaction. That is, the PO43- ion accepts a proton, which means that it is acting as a base. 1.2.1 Bronsted-Lowery Acid-Base Reactions: Conjugate Acids and Bases: Conjugate Acid: When a proton (not a hydrogen atom or â€Å"hydrogen† but a proton, H+) is added to a molecule or ion, its conjugate acid forms. Exampl... ...near to neutral if not that particular drug or medicine may cause irritation in body tissues. †¢ Fermentation process requires a specific pH for the best results. The pH during a fermentation process changes by itself due to fermentation process so buffer play important role in controlling this pH change. †¢ Buffers are also used in foods to maintain the acidity of the food in order to preserve the flavour and appearance of food. †¢ Dyes in textile industries play an important role in giving colour to different fabrics. Colour strength of dyes is closely associated to narrow pH range which is maintained by using different buffer systems. pH above or below this narrow range will affect the colour imparting ability of different dyes. †¢ In Leather industries narrow range of pH control of tanning and dyeing baths determine the texture and colour of the finished product.