Core Chemistry - Topic 3 Acids

• Indigestion - stomach producing too much acid
• Heartburn - acid escaping from the top of the stomach

• Stomach acid - Hydrochloric Acid ( HCl )
• Digestive enzymes need acid conditions to work
• Antacids neutralise excess stomach acid
  • they contain bases (stubstances that react with acid)
• Some bases are soluble
  • base dissolved in water - alkali
• Acid or alkali? - Indicator

acid + base ➝ salt + water

hydrochloic acid + calcium carbonate ➝ calcium chloride + water + carbon dioxide

      2HCl (aq)      +      CaCO3 (s)       ➝      CaCl2 (aq)      + H2O (l) +    CO2 (g)

• Types of compounds to neutralise acid
  • metal oxides, metal hydroxides and metal carbonates

• To manage spilt acid or alkali safely
• • dilute with water
  • neutralise it with metal compound

acid + metal oxide ➝ salt + water

acid + metal hydroxide ➝ salt + water

acid + metal carbonate ➝ salt + water + carbon dioxide

• Yellow-green toxic gas with many uses
  • killing microorganisms - treating our water supply
  • manufacture bleach/other cleaning products
  • manufacture plastics e.g. polychlorothene (PVC)
• Harmful to living things
• Reacts with many coloured substances converting them to colourless

• Potential problems
  • gas leak from a chemical factory
  • gas-carrying tanker involved in an accident
  • leaking toxic gas kills more people than an explosion

• TEST FOR CHLORINE
  • damp blue litmus paper - red then bleached white
  • acidic = red       chlorine = bleached white

• Some substances can be decomposed using electrical energy or heat energy
• Decomposition of compounds can form new compounds
  • using heat THERMAL DECOMPOSITION
  • using electricity ELECTROLYSIS called electrolytes
• Direct current passed through sea water
  • chlorine gas is produced
• Direct current passed through dilute hydrochloric acid
  • hyrodgen gas chlorine gas are produced
• Direct current passed through water
  • hydrogen gas and oxygen are given off

• Hydrogen
  • used as rocket fuel (pure hydrogen)
  • lightest gas
• Oxygen - mixed with fuel to make flames very hot