Acids and bases


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A short and simple guide to acid-base reactions. Explains broadly what is a base and acid, as well as substances with basic and acidic properties

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Acids and bases

  1. 1. ACIDS AND BASESUsually we define acids as substances which dissolve in water to produce H+ ions.An important property of acids is that it turns blue litmus red.AcidsThere are 2 different kinds of acids- strong acids- weak acidsStrong acids dissolve completely in water to form H+ ions and negative ions Dissolving works because water is very good at attracting ions to separate from their compounds. Notice that bonding in the first place is due to attraction between neighbour particles… So if the attraction from the surrounding water molecules ishigher, the particles will actually break away from itsexisting structure to be surrounded by water molecules!Litmus is itself a weak acid which we callHLit. As aweak acid does not fully dissociate in water to produce H+ ions and Lit- ions, both Lit- andHLit are present in litmus paper or solution.When hydroxide ion is added, more Lit- are formed HLit reacts with hydroxide ions in aneutralisation reaction to form H2O and Lit-
  2. 2. Ph scale The pH scale measures how acidic or basic a substance is and it ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. Acid-base reactions for acids Acids can react with- metalsto form salt and hydrogen- carbonates to form salt, carbon dioxide and water- bases to form salt and waterAcid-base reactions for substances with acidic propertiesThe interesting thing about acid-base reactions is how acidic stuffare attracted to react withbase just like how boys like girls and vice versa.
  3. 3. On one hand you have a base, which is always made up of metal ions, and one of thefollowing ions1) OH- ion2) oxideionAnd any substances with acidic properties love to react with these 3 ions! Such substancesare always non-metal in the form of the following1) non-metal oxides2) acids (contains H atoms, like HCl and HNO3)You might be familiar with carbonates acting as a base in reactions with acids. Whilecarbonates have basic properties, they are actually formed from acid-base reaction involvingcarbon dioxide and a metal oxide or hydroxide!Tea is very slightly acidic as well but much less acidic than carbonated soft drinks!Coffee is acidic tooIn fact, citric acid is used to both flavour and preserve soft drinksToothpaste contain alkali to neutralise the acidic plaque