Topic 4 - Chemical Change

• What is oxidation?

  When a substance gains oxygen
• What is reduction?

  When a substance loses oxygen
• What does the reactivity series of metals show?

  The metals in order of their reactivity
• What happens to metals above hydrogen in the reactivity series when they react with acid?

  They produce hydrogen gas
• How does the reactivity of metals with acid change?

  The more reactive, the quicker and more violent the reaction
• Do metals below hydrogen react with acids?

  No, they don’t react with acids
• Which metals typically react with water?

  Mostly Group I and II metals
• What is a displacement reaction?

  A more reactive metal displaces a less reactive metal
• How are unreactive metals found in Earth?

  In their natural state
• How can metals less reactive than carbon be extracted?

  Reduction with carbon
• What happens during the reduction of metal oxide with carbon?

  Carbon displaces the metal and gets oxidised
• How are metals more reactive than carbon extracted?

  By electrolysis
• How are oxidation and reduction defined in terms of electron transfer?

  Oxidation is loss of electrons, reduction is gain
• What is the general equation for a reaction between metals and acids?

  Metal + acid → salt + hydrogen
• What type of reaction is the reaction between metals and acids?

  Redox reaction and displacement reaction
• Which metals in the reactivity series will react with acid?

  Those above hydrogen
• What is the general equation for a neutralisation reaction?

  Base + acid → salt + water
• What is the general equation for the reaction between metal carbonate and acid?

  Metal carbonate + acid → salt + water + carbon dioxide
• What is the general equation for the reaction between metal oxides and acids?

  Metal oxide + acid → salt + water
• What is a redox reaction?

  A reaction where both oxidation and reduction occurs
• In the reaction of magnesium with hydrochloric acid, which species is oxidised?

  Magnesium, as it loses electrons
• In the reaction of magnesium with hydrochloric acid, which species is reduced?

  Hydrogen, as it gains electrons
• How is a soluble salt formed?

  • React excess acid with insoluble chemical (e.g., metal oxide)
  • Filter off leftovers
  • Crystallise the product
• What do acids produce in aqueous solutions?

  Hydrogen ions
• What do alkalis produce in aqueous solutions?

  Hydroxide ions
• What are bases, acids, and alkalis?

  • Bases neutralise acids
  • Acids produce hydrogen ions in solutions
  • Alkalis are soluble bases producing hydroxide ions in solutions
• What is the pH scale?

  A measure of acidity/alkalinity of a solution
• What does a pH of 7 indicate?

  Neutral solution
• What is the short ionic form of the general equation for a neutralisation reaction?

  H+ + OH− → H2O
• What is a strong acid?

  Completely ionised in aqueous solution
• What is a weak acid?

  Partially ionised in aqueous solution
• What happens to pH as the concentration of H+ increases?

  The pH decreases
• What is the difference between concentrated and diluted acids?

  • Concentrated acid has more moles of acid per unit volume
  • Dilute refers to solutions of low concentrations
  • Concentration is not the same as strength
• What happens to hydrogen ion concentration as pH decreases by one unit?

  Increases by a factor of 10
• Name the following salts: LiNO3, K2CO3, MgBr2, BaSO4.

  • LiNO3: Lithium nitrate
  • K2CO3: Potassium carbonate
  • MgBr2: Magnesium bromide
  • BaSO4: Barium sulfate
• What is electrolysis?

  Passing electric current through ionic substances
• What is an electrolyte?

  The liquid/solution which conducts electricity
• What is a cathode?

  The negative electrode
• What is an anode?

  The positive electrode
• What occurs at the cathode during electrolysis?

  Reduction occurs