Acids and bases

    Cards (21)

    • Properties of acids
      Turn universal indicator from green to red pH is less than 7
      usually react with metals to form salts
      turn blue litmus paper red
      sour
      corrosive when concentrated
      dissolve in water to produce hydrogen ions
    • Common acids
      Hydrochloric acid HCl
      Nitric acid HNO3
      Sulphuric acid H2SO4
    • Properties of alkalis
      Soapy to the touch
      soluble bases
      turns universal indicator paper from green to purple or blue
      turn red litmus blue
      bitter
      dissolve in water to produce hydroxide ions
    • Common alkalis
      Sodium hydroxide NaOH
      Calcium hydroxide Ca(OH)2
      ammonia NH3
    • pH meter
      Electronic instrument that measures the pH of a substance, consists of a glass electrode attached to an electronic reader which gives a reading to one decimal place
    • Litmus
      Red litmus. Blue litmus
      Acidic solution stays red. turns red
      neutral solution stays red. stays blue
      alkaline solution turns blue. Stays blue
    • Methyl orange
      Turns red In acid
      stays yellow in neutral and alkali
    • Phenolphthalein
      Colourless in acid and neutral
      pink in alkali
    • Strong acid
      Completely ionised in water
      concentration of a chemical solution refers to the amount of solute that is dissolved in a solvent
      nearly all the acid molecules form h+ ions
      in a weak acid only some do
      the higher the concentration of hydrogen ions in a solution the lower the pH
    • Strong alkali
      Completely ionised in water
      nearly all the alkali molecules form OH- ions
      the higher the concentration of hydroxide ions in an alkali solution the higher the pH
    • Neutralisation
      Involves the reaction of a base or alkali with an acid to make salt and water
    • Making of a salt
      When an acid reacts with an alkali it produces salt and water
      the alkali has neutralised the acid by removing its h+ ions and turning them into water
    • salt
      A salt is a compound formed when some or all of the hydrogen ions in an acid are replaced by metal ions or ammonium ions
    • Word equations for reactions of acids
      Acid + metal -> salt + hydrogen
      acid + alkali -> salt + water
      acid + metal oxide -> salt + water
      acid + metal carbonate -> salt + water + carbon dioxide
      acid + metal hydrogen carbonate -> salt + water + carbon dioxide
    • Making a salt using an acid and a solid
      1. Place 25cm3 of dilute sulfate in beaker
      2. slowly add an excess of black copper ll oxide stirring and heating gently
      3. reaction is complete when no more base dissolves, excess base is used to ensure all acid has reacted
      4. filter mixture
      5. dispose of residue and keep filtrate, blue solution of the salt in water
      6. pour into evaporating basin, heat to evaporate water and reduce volume by half to leave it to cool and crystallise dry crystals between filter paper
    • Titration
      1. Prepare Burette and fill with hydrochloric acid
      2. pipettes 25cm3 of sodium hydroxide into a conicalflask using a pipette filler
      3. Add 3 drops of phenolphthalein and add acid from burette and swirl gently to mix solutions
      4. Stop adding when it has turned from pink to colourless
      5. record volume of acid added
      6. repeat with fresh samples until two results are obtained that differ less than 0.1cm 3
    • Soil treatment
      If soil is too acidic it is treated with base to neutralise it
    • Indigestion
      Have hydrochloric acid in our stomach but too much leads to indigestion so we neutralise it with a base
    • Insect stings
      Bee stings contain acid so rub it with base
      wasp stings are alkaline so we need acid
    • Test for hydrogen gas
      Apply lighted splint into a test tube filled with hydrogen and it should make a squeaky pop
    • Test for carbon dioxide
      Limewater/ calcium hydroxide is put in a test tube and carbon dioxide is bubbled through it
      limewater will turn from colourless to milky white if carbon dioxide is present (calcium carbonate is formed)
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