ACIDS AND BASES

What is acid? a substance that ionizes in water to produce hydrogen ions, H + What is base? a substance that reacts with an acid to form only salt and water What is alkali? Soluble bases that produce OH ¯ ions in water

Chemical properties of acid Sour taste pH less than 7 Corrosive Conduct electricity Acid can react with a) bases to produce salts and water b) metals to produce salts and hydrogen gas c) carbonates to produce salts, carbon dioxide gas and water

Chemical properties of base Bitter/smooth/soapy pH more than 7 Corrosive Conduct electricity Base can react with a)Acid to produce a salt and water b)Heated with ammonium salt to produce ammonia gas

Uses of acids in daily life Sulphuric acid – paints, detegents, polymers, fertilisers Carbonic acid- make carbonated drinks Ethanoic acid- vinegar Uses of base in daily life Sodium hydroxide – soaps, detergents, bleaching agents Magnesium hydroxide – toothpaste Ammonia- fertilisers

Role of water in the formation of hydrogen ions In the presence of water, an acid will ionize to form the hydrogen ions, H + So, water is essential for the formation of hydrogen ions that cause acidity

Role of water in the formation of hydroxide ions In the presence of water, alkali will dissociate to form hydroxide ions, OH¯ Hence, water is essential for the formation of hydroxide ions that cause alkalinity

pH scale

A set of numbers used to show the degree of acidity and alkalinity of a solution pH values of less than 7 indicates an acidic solution pH values of more than 7 indicates an alkaline solution pH values of 7 indicates a neutral solution pH scale

pH values Higher pH value more alkaline higher concentration of hydroxide ion Lower pH value more acidic higher concentration of hydrogen ion When acids meets base

pH is actually a measurement of the concentration of hydrogen, H + in a solution The higher the concentration of the H + ions, the lower the pH value, and more acidic the solution is The higher the concentration of the OH¯ ions, the higher the pH value and the more alkaline solution the solution is. pH values

Acid  Strong acid is an acid that dissociate (ionize ) completely in water to form hydrogen ion,H + of high concentration  Weak acid is an acid that dissociate (ionize ) partially in water to produce hydrogen ions,H + of low concentration. Mineral acids such as hydrochloric acid, nitric acid, and sulphuric acid are strong acids Weak acids-ethanoic acid, methanoic acid, citric acid, tartaric acid

Alkali  Strong alkali is produce when a base dissociates completely in water to produce hydroxide ions, OH - of high concentration  Weak alkali is produced when a base dissociates partially to produce hydroxide ions, OH - of low concentration. Strong alkali- sodium hydroxide, potassium hydroxide Weak alkali- ammonia solution