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ACIDS AND BASES

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

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ACIDS AND BASES

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  1. ACIDS ANDBASES

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. pH scale

  9. 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

  10. 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

  11. pH values • 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.

  12. Acid • Strong acidis an acid that dissociate (ionize ) completely in water to form hydrogen ion,H+ of high concentration • Weak acidis 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

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

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