gcse recap

• What is formed when a substance is dissolved in water?

  An aqueous solution
• What do acids release when added to water?

  Protons, H+ ions
• What is the general reaction for hydrochloric acid in water?

  HCl(g) → H+(aq) + Cl-(aq)
• How do acids taste?

  Taste very sour
• Name an example of a common acid.

  Hydrochloric acid
• What are bases defined as?

  Substances that neutralise acids
• What do bases do in terms of protons?

  They are proton acceptors
• What are alkalis?

  Specific bases soluble in water
• What ions do alkalis form in water?

  Hydroxide, OH- ions
• What is the ionic equation for neutralization?

  H+ + OH- → H2O
• What do indicators measure?

  The pH or pH range of a solution
• What do different indicators contain?

  Different dyes that change colour
• Why is universal indicator useful?

  It has a wide range of colours
• What colour does universal indicator turn at pH 0-1?

  Red
• What colour does universal indicator turn at pH 7?

  Green
• What colour does universal indicator turn at pH 11-14?

  Purple
• What happens to most elements when heated with oxygen?

  They react to form oxides
• What is the test for oxygen?

  A glowing splint will re-light
• What are metal oxides classified as?

  Basic oxides
• What do most metal oxides do?

  Neutralise acids
• What are examples of soluble metal oxides?

  Sodium oxide, Potassium oxide
• What do non-metal oxides react with water to form?

  Acidic solutions
• What is the reaction of carbon dioxide with water?

  Carbon dioxide + water → carbonic acid
• What is the reaction of sulphur dioxide with water?

  Sulphur dioxide + water → sulphurous acid
• How can elements be classified based on their oxides?

  As metal or non-metal based on oxide type
• What are the general reactions to make salts?

  • Acid + Alkali → Salt + Water
  • Acid + Base → Salt + Water
  • Acid + Metal → Salt + Hydrogen
  • Acid + Metal Carbonate → Salt + Water + Carbon Dioxide
• What is required for a metal to react with an acid to form a salt?

  The metal must be more reactive than hydrogen
• How do we identify hydrogen gas in a reaction?

  Lit splint makes a squeaky pop
• What happens when an acid reacts with a base?

  It forms a salt plus water
• What is the result of reacting an acid with a metal oxide?

  Salt plus water
• What is produced when an acid reacts with a metal carbonate?

  Salt plus water plus carbon dioxide
• How are salts named based on acids?

  • Hydrochloric acid → chloride salts
  • Nitric acid → nitrate salts
  • Sulphuric acid → sulphate salts
  • Phosphoric acid → phosphate salts
• What is the formula for magnesium chloride?

  MgCl2
• What is the overall charge of any chemical compound?

  Zero
• What is the formula for aluminium sulphate?

  Al2(SO4)3
• What are the key positive ions (cations) to know?

  • Magnesium = Mg2+
  • Calcium = Ca2+
  • Silver = Ag+
  • Lead = Pb2+
  • Sodium = Na+
  • Aluminium = Al3+
  • Potassium = K+
  • Copper (I) = Cu+
  • Copper (II) = Cu2+
  • Ammonium = NH4+
• What are the key negative ions (anions) to know?

  • Chloride = Cl-
  • Sulphate = SO4^2-
  • Nitrate = NO3-
  • Bromide = Br-
  • Hydroxide = OH-
  • Iodide = I-
• What is the state symbol for solid?


  (s)
• What is the state symbol for liquid?

  (l)
• What is the state symbol for aqueous solutions?

  (aq)