chap1. acids & bases

• An acid is substance which reacts with a base to form salt and water.

  e.g. hydrochloric acid + sodium hydroxide → sodium chloride + water

  Reactions of Acids

  The following are typical reactions of acids:

  Alkali + acid = salt + water

  Base + acid = salt + water

  Carbonate + acid = salt + water + carbon dioxide

  Metal + acid = salt + hydrogen

  What pattern can you see in the typical reactions of acids?

  ABCM

  A typical acid reaction (with Alkalis, Bases, Metal Carbonates & Metals) will always produce a salt and other products.
• Describe the test for hydrogen gas:

  Test: Lighted splint

  Result: Extinguished with a 'pop' sound
• Describe the test for carbon dioxide:

  Test: Bubble the gas through limewater

  Result: A white precipitate is formed
• alkalis are special bases that can dissolve in water
• hydrochloric acid + sodium hydroxide = sodium chloride + water
• litmus paper changes colour when in contact with acid
• bases contain the word oxide

  alkalis contain the word hydroxide (except aqueous ammonia)
• acids:

  hydrochloric

  nitric

  sulfuric

  ethanoic
• alkali elements are on the left of the periodic table
• thymophthalien test turns blue at pH 10 and colourless otheriwse
• methyl orange test

  acids: red orange

  neutral and alkali: yellow
• acids: sour and Corrosive

  akali: bitter and slippery
• sulfuric=sulfate

  hydrochloric=chloride

  nitric=nitrate
• erode stone

  corrode metal
• 1. An acid is substance which reacts with a base to form salt and water. 2. The reaction between an acid and a base is termed as neutralisation. 3. A base is a metal oxide or a metal hydroxide 4. An alkali is a soluble base. 5. Metal + acid → salt + hydrogen 6. Ammonium salt + alkali → salt + water + ammonia gas 7. Alkalis turn universal indicator blue/purple. 8. Acids turn moist blue litmus red. 9. A strong acid has a pH lower than a weak acid.
• When iron rusts, structures such as bridges become corroded and unsafe. These structures need to be repaired and replaced. Rusting causes the loss of finite natural resources such as metals
• Decomposition of food leads to waste
• Many crops grow better in soil that is neutral and not acidic. Excess acidity from soil can be removed by adding limestone, ( containing calcium carbonate, CaCO3 ), or lime, ( containing calcium oxide, CaO ), which neutralises the acid
• Sodium hydroxide is used in making soaps. Ammonia solution is used to make fertilisers.
• Salts made from strong acid and strong base

  Neutral salt solution
• Salts made from strong acid and weak base

  Acidic salt solution
• Salts made from weak acid and strong base


  Basic salt solution