Reactivity Series

• The chemistry of the metals is studied by analysing their reactions with water and acids

  • Based on these reactions a reactivity series of metals can be produced
  • The series can be used to place a group of metals in order of reactivity based on the observations of their reactions with water and acids
• The non-metals hydrogen and carbon are also included in the reactivity series as they are used to extract metals from their oxides
• Reactivity Series of Metals

  A) violently

  B) violently

  C) quickly in air

  D) quickly

  E) violently

  F) quickly In air

  G) less strongly

  H) vigorously

  I) readily

  J) slow reaction (reacts with steam)

  K) vigorously

  L) readily

  M) readily

  N) readily

  O) very slow reaction (reacts slowly with steam)

  P) less strongly

  Q) reacts

  R) no reaction with water or steam

  S) no reaction

  T) reacts

  U) no reaction

  
• Observations from the table above allow the following reactivity series to be deduced
• Reactivity Series Mnemonic

  A) please

  B) stop

  C) calling

  D) me

  E) a

  F) careless

  G) zebra

  H) instead

  I) try learning

  J) how

  K) copper

  L) saves

  M) gold

  
• The more reactive metals will react with cold water to form a metal hydroxide and hydrogen gas
• Potassium, sodium and calcium all undergo reactions with cold water as they are the most reactive metals: metal + water →  metal hydroxide + hydrogen

  • For example, calcium and potassium:
  • Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g)
  • 2K (s) + 2H2O (l) → 2KOH (aq) + H2 (g)
• Metals just below calcium in the reactivity series do not react with cold water but will react with steam to form a metal oxide and hydrogen gas, for example, magnesium:

  • Mg (s) + H2O (g)  →  MgO (s) + H2 (g)
• Only metals above hydrogen in the reactivity series will react with dilute acids

  • Unreactive metals below hydrogen, such as gold, silver and copper, do not react with acids
  • The more reactive the metal then the more vigorous the reaction will be
• Metals that are placed high on the reactivity series such as potassium and sodium are very dangerous and react explosively with acids
• When acids react with metals they form a salt and hydrogen gas

  • The general equation is: metal + acid ⟶ salt + hydrogen
• Some examples of metal-acid reactions and their equations are given below:

  A) MgSO4 + H2

  B) MgCl2 + H2

  C) ZnSO4 + H2

  D) ZnCl2 + H2

  E) FeSO4 + H2

  F) FeCl2 + H2

  
• Some reactive metals, such as the alkali metals, react easily with oxygen

  • Silver, copper and iron can also react with oxygen although much more slowly
  • When metals react with oxygen a metal oxide is formed, for example, copper: metal + oxygen → metal oxide
  • 2Cu (s) + O2 (g) → 2CuO (s)
  • Gold does not react with oxygen
• The order of reactivity of metals can be deduced by making experimental observations of reactions between metals and water, acids and oxygen

  • The more vigorous the reaction of the metal, the higher up the reactivity series the metal is
• A combination of reactions may be needed, for example, the order of reactivity of the more reactive metals can be determined by their reactions with water

  • The less reactive metals react slowly or not at all with water, so the order of reactivity would need to be determined by observing their reactions with dilute acid
• Temperature change in a reaction can also be used to determine the order of reactivity

  • The greater the temperature change in a reaction involving a metal, the more reactive the metal is
• When metals react with other substances, the metal atoms lose electrons to form positive ions
• Metal atoms form positive ions by loss of electrons when they react with other substances

  • The tendency of a metal to lose electrons is a measure of how reactive the metal is
• A metal that is high up on the series loses electrons easily and is thus more reactive than one which is lower down on the series
• Any metal will displace another metal that is below it in the reactivity series from a solution of one of its salts

  • This is because more reactive metals lose electrons and form ions more readily than less reactive metals, making them better reducing agents
  • The less reactive metal is a better electron acceptor than the more reactive metal, thus the less reactive metal is reduced. (OIL-RIG: reduction is gain of electrons)l
  • Example: Magnesium + copper sulfate
• Magnesium is a reactive metal and can displace copper from a copper sulfate solution

  • Magnesium loses its electrons more easily and the ion of the less reactive metal, copper, will gain these electrons to form elemental copper
  • This is easily seen as the more reactive metal slowly disappears from the solution, displacing the less reactive metal
  • magnesium + copper sulfate → magnesium sulfate + copper
  • Mg (s) + CuSO4 (aq) → MgSO4 (aq) + Cu (s)
• The blue colour of the CuSO4 solution fades as colourless magnesium sulfate solution is formed

  • Copper coats the surface of the magnesium and also forms solid metal which falls to the bottom of the beaker
• Diagram showing the colour change when magnesium displaces copper from copper sulfate

  A) blue copper

  B) sulfate

  C) magnesium

  D) magnesium

  E) powder

  F) copper

  G) sulfate

  H) stirred

  I) magnesium sulfate

  J) copper

  K) colorless

  L) magnesium

  M) sulfate

  N) copper

  
• By combining different metals and metal salts solutions it is possible to come up with a relative reactivity order
• Metal Solutions Displacement Table

  A) magnesium sulfate

  B) iron

  C) zinc chloride

  D) iron

  E) iron nitrate

  F) silver

  G) no reaction

  
• From this table we can deduce the order of reactivity:

  • Magnesium and zinc are both more reactive than iron but magnesium is more reactive than zinc
  • Copper and silver are both less reactive than iron but silver is less reactive than copper
• The order of reactivity of the metals tested can be therefore be deduced as:

  • Mg > Zn > Fe > Cu > Ag
• Aluminium is high in the reactivity series, but in reality, it does not react with water and the reaction with dilute acids can be quite slow

  • This is because it reacts readily with oxygen, forming a protective layer of aluminium oxide which is very thin
  • This layer prevents reaction with water and dilute acids, so aluminium can behave as if it is unreactive
• Reactivity of metals with oxygen, water, and acid

  A) burn in oxygen

  B) tarnish

  C) metal oxide

  D) surface

  E) burn

  F) no reaction

  G) fizzes

  H) cold water

  I) no reaction

  J) fizzes

  K) no reaction

  
• Metal + oxygen → metal oxide
• Metal + acid → salt + hydrogen
• Metal + water → metal hydroxide + hydrogen
• Displacement reactions - a more reactive metal displaces a less reactive metal froma. compound
• Reaction of magnesium and steam

  • creates an oxide and hydrogen
  • Mg + H2O (g) → MgO + H2
• Experiment to find hydrogen

  • metals below hydrogen do not react with water or steam
  • metals from magnesium to iron react with steam to produce metal oxides and hydrogen

  A) mineral wool

  B) water

  C) metal

  D) heat

  E) hydrogen

  F) reaction

  G) water

  
• Displacement Reaction

  A) blue

  B) copper sulfate

  C) blue colour fades

  D) colourless

  E) magnesium

  F) magnesium

  G) copper

  
• The reactions with O2, water and HCl show that iron is more reactive than Cu

  • iron and copper are competing for oxygen and iron wins
  • Iron  +  Copper (II) Oxide  ®  Iron (II) Oxide  +  Copper

  
• A more reactive metal has a greater tending to form a metal ion by losing electrons than a less reactive metal
• In a displacement reaction, a more reactive metal will displace a less reactive metal from a solution of its salt
• Ionic equation of zinc solid and copper solution

  • Zn (s) + Cu 2+ (aq) → Zn 2+ (aq) + Cu (s)
  • the charge from the metal in the compound is given to the metal that replaces it
  • this is also a redox reaction