acids, bases and salts

• Acids have a sour taste
• Acids conducts electricity
• Acids have a pH of <7
• Acids turns blue litmus paper red
• reactive metal + acid -> salt + hydrogen gas
• carbonate + acid -> salt + carbon dioxide + water
• base/alkali + acid -> salt + water
• strong acids completely ionise in water to form high concentration of H+ ions
• weak acids partially ionise in water to form low concentration of H+ ions
• HCl and HNO3 are monobasic
• H2SO4 is dibasic
• H3PO4 is tribasic
• what metals are unreactive to dilute acids

  copper, silver and gold
• how to test for hydrogen gas ?

  it extinguishes a lighted splint with a ’pop’ sound
• how to test for carbon dioxide gas ?

  it forms a white ppt in limewater (calcium hydroxide)
• soluble bases (alkali)


  metal oxides (1BC):

  group 1 oxides, calcium oxide and barium oxide

  metal hydroxides (1ABC):

  group 1 hydroxide, calcium hydroxide, barium hydroxide and aqueous ammonia
• calcium oxides are alkali

  yes
• sodium oxide is an insoluble base

  no
• soluble metal oxides dissolve in water to form metal hydroxides (alkalis)
• alkalis have a bitter tase
• alkalis have a soapy feeling
• alkalis have pH >7
• alkalis turns red litmus paper blue
• alkali + ammonia salt -> salt + ammonia + water
• test for ammonia

  it turns damp red litmus paper blue
• soil that is overly acidic can be teated with bases such as calcium hydroxide/ adding calcium carbonate, producing carbon dioxide
• amphoteric oxides behave as a base when it reacts with an acid and behaves as an acid when it reacts with an alkali
• amphoteric oxides

  (ZAP)

  zinc oxide, aluminium oxide, lead (II) oxide
• metal oxides are either basic or amphoteric
• non- metal oxides are either acidic or neutral
• neutral oxides

  (NO COld H2O)

  nitrogen monoxide, carbon monoxide, water
• what are acids ?

  substances which produces hydrogen ions when dissolved in water and tend to show an orange or red colour using universal indicator
• what are alkali ?

  they are soluble bases which produces hydroxide ions when dissolved in water, and tend to show a blue or purple colour using universal indicator
• pH of weak acids

  3- 7
• pH of strong acids

  1-3
• pH of weak alkali

  7-10
• pH of strong alkali

  10-14
• what‘s the difference between strong and weak acids ?

  strong acids ionise completely in water to form a high concentration of H+ ions while weak acids ionise partially in water to form a low concentration of H+ ions
• what is this reaction of H+ + OH- -> H2O called ?

  neutralisation
• what is neutralisation ?

  it is the reaction between hydrogen ions and hydroxide ions to produce water