Definitions

• Acid:

  • Acids produce hydrogen ions (H+) in aqueous solutions
  • pH range of 0-6
• Alkali:

  • Alkalis produce hydroxide ions (OH-) in aqueous solutions
  • pH range of 8-14
• Crystallisation:

  • Separation technique to produce solid crystals from a solution by evaporating the solvent
• Displacement:

  • A chemical reaction where a more reactive element displaces a less reactive element from its compound
• Electrolysis:

  • Splitting up of an ionic compound using electricity
  • Chemical reactions occur at the electrodes and materials decompose
• Electrolyte:

  • Solution containing free ions from molten or dissolved ionic substance
  • Ions are free to move to carry charge
• Extraction:

  • Techniques used to separate a desired substance when mixed with others
• Filtration:

  • Separation technique to separate solids from liquids
• Negative electrode (cathode):

  • Electrode where hydrogen is produced if the metal in the electrolyte is more reactive than hydrogen
  • Positively charged ions gain electrons, reactions are reductions
• Neutralisation:

  • Reaction when an acid and a base react to form water and a salt
• Oxidation:

  • Reaction involving the gain of oxygen
  • Loss of electrons
• pH scale:

  • Measure of acidity or alkalinity of a solution from 0 to 14
  • Can be measured using universal indicator or a pH probe
• Positive electrode (anode):

  • Electrode where oxygen is produced unless the solution contains halide ions, then the halogen is produced
  • Negatively charged ions lose electrons, reactions are oxidations
• Reduction:

  • Reaction involving the loss of oxygen
  • Gain of electrons
• Reduction with carbon:

  • Metals less reactive than carbon can be extracted from their oxides by reduction with carbon
• Strong acid:

  • Completely ionised in aqueous solution
  • Examples: hydrochloric, nitric, and sulfuric acids
• Reactivity series:

  • Metals arranged in order of reactivity
  • Used to predict products from reactions
• Universal indicator:

  • Mixture of dyes that changes color gradually over a range of pH
  • Used in testing for acids and alkalis
• Weak acid:

  • Partially ionised in aqueous solution
  • Examples: ethanoic, citric, and carbonic acids
• Redox reaction:

  • Reaction where both oxidation and reduction occur simultaneously
• Titration:

  • Technique using a solution of known concentration to determine the concentration of an unknown solution