5.1 Reactivity and displacement reactions

• Reactivity: Reactivity refers to the tendency of a substance to undergo chemical reactions, often characterized by its ability to lose or gain electrons and form new compounds. It reflects how readily a substance participates in chemical reactions under specific conditions.
• Reactivity series: The reactivity series is a list of metals arranged in order of their relative reactivity, with the most reactive metal at the top and the least reactive metal at the bottom. This series is a useful tool in predicting the outcomes of displacement reactions, where a more reactive metal displaces a less reactive metal from its compound in solution.
• Displacement reaction: A displacement reaction occurs when an element replaces another element from a compound. In this type of reaction, one element (the displacer) takes the place of another element (the displacee). Displacement reactions are important because they allow us to extract elements from their compounds.
• Reactivity Series:

  Potassium, K

  Sodium, Na

  Calcium, Ca

  Magnesium, Mg

  Aluminium, Al

  Zinc, Zn

  Iron, Fe

  Lead, Pb

  Copper, Cu

  Silver, Ag

  Gold, Au
• Reactivity series is a list of metals arranged in order of their relative reactivity
• Provides a ranking of metals based on their tendency to lose electrons and form positive ions in chemical reactions
• Most reactive metals are listed at the top of the series, while the least reactive metals are at the bottom
• Metals higher in the reactivity series tend to react more readily with acids and water
• Metals lower in the series are less reactive and often do not react with acids and water under normal conditions
• Reactivity series is useful in predicting outcomes of displacement reactions
• Reactivity series helps in determining the feasibility of various chemical reactions involving metals
• Potassium (K):

  • Reaction with water: Potassium reacts vigorously with water, producing hydrogen gas and forming potassium hydroxide (KOH). The reaction is highly exothermic, often resulting in the formation of a lilac flame.
  • Reaction with oxygen: Potassium reacts rapidly with oxygen, forming potassium oxide (K2O).
  • Reaction with dilute acid: Potassium reacts with dilute acids to liberate hydrogen gas and form potassium salts.
• Sodium (Na):

  • Reaction with water: Sodium also reacts vigorously with water, producing hydrogen gas and forming sodium hydroxide (NaOH).
  • Reaction with oxygen: Sodium reacts with oxygen to form sodium oxide (Na2O).
  • Reaction with dilute acid: Sodium reacts similarly to potassium with dilute acids, producing hydrogen gas and forming sodium salts.
• Calcium (Ca):

  • Reaction with water: Calcium reacts with water, albeit less vigorously than sodium and potassium. It produces hydrogen gas and forms calcium hydroxide (Ca(OH)2).
  • Reaction with oxygen: Calcium readily reacts with oxygen to form calcium oxide (CaO), also known as quicklime.
  • Reaction with dilute acid: Calcium reacts with dilute acids to liberate hydrogen gas and form calcium salts.
• Magnesium (Mg):

  • Reaction with water: Magnesium has a very slow reaction with cold water but reacts rapidly with steam to produce hydrogen gas and magnesium hydroxide (Mg(OH)2).
  • Reaction with oxygen: Magnesium burns in oxygen with a bright white flame to form magnesium oxide (MgO).
  • Reaction with dilute acid: Magnesium reacts with dilute acids to liberate hydrogen gas and form magnesium salts.
• Aluminium (Al):

  • Reaction with water: Aluminium does not react with water at room temperature due to the formation of a protective oxide layer on its surface.
  • Reaction with oxygen: Aluminium forms a thin oxide layer when exposed to oxygen, preventing further reaction.
  • Reaction with dilute acid: Aluminium reacts slowly with dilute acids, releasing hydrogen gas and forming aluminium salts.
• Zinc (Zn):

  • Reaction with water: Zinc does not react with water under normal conditions.
  • Reaction with oxygen: Zinc reacts slowly with oxygen, forming zinc oxide (ZnO).
  • Reaction with dilute acid: Zinc reacts with dilute acids, producing hydrogen gas and forming zinc salts.
• Iron (Fe):

  • Reaction with water: Iron does not react with water at room temperature.
  • Reaction with oxygen: Iron reacts with oxygen to form iron oxide (Fe2O3 or Fe3O4), commonly known as rust.
  • Reaction with dilute acid: Iron reacts with dilute acids, liberating hydrogen gas and forming iron salts.
• Lead (Pb):

  • Reaction with water: Lead does not react with water at room temperature.
  • Reaction with oxygen: Lead forms a protective layer of oxide when exposed to oxygen, preventing further reaction.
  • Reaction with dilute acid: Lead reacts slowly with dilute acids, releasing hydrogen gas and forming lead salts.
• Copper (Cu):

  • Reaction with water: Copper does not react with water under normal conditions.
  • Reaction with oxygen: Copper reacts with oxygen to form copper oxide (Cu2O or CuO), depending on the conditions.
  • Reaction with dilute acid: Copper does not react with dilute acids at room temperature.
• Silver (Ag):

  • Reaction with water: Silver does not react with water.
  • Reaction with oxygen: Silver does not react with oxygen at room temperature.
  • Reaction with dilute acid: Silver does not react with dilute acids under normal conditions.
• Gold (Au):

  • Reaction with water: Gold does not react with water.
  • Reaction with oxygen: Gold does not react with oxygen at room temperature.
  • Reaction with dilute acid: Gold does not react with dilute acids under normal conditions.
• Reaction Description: When a clean iron nail is placed in a beaker containing copper sulfate solution, a displacement reaction occurs. The blue color of the copper sulfate solution fades slightly, indicating a chemical change. Additionally, the iron nail becomes coated with a layer of copper, giving it a copper-colored appearance.
• Equation:

  • Word Equation: Copper sulfate + Iron → Iron sulfate + Copper
  • Symbol Equation: CuSO4 + Fe → FeSO4 + Cu
• Explanation:

  • Iron, being more reactive than copper, displaces copper from the copper sulfate solution.
  • The iron atoms from the nail react with the copper ions (Cu^2+) in the solution, causing copper to deposit onto the surface of the iron nail.
  • Simultaneously, the iron atoms lose electrons and form iron ions (Fe^2+), which combine with sulfate ions (SO4^2-) from the copper sulfate to form iron sulfate (FeSO4).
  • This displacement reaction results in a change in color of both the solution and the iron nail.
• Implications:

  • The displaced copper forms a thin layer on the surface of the iron nail, giving it a copper-colored appearance.
  • The iron sulfate formed remains in the solution, contributing to the slight change in color observed.
• General Principle:

  • Displacement reactions occur when a more reactive element displaces a less reactive element from its compound.
  • In this case, iron, being more reactive than copper, displaces copper from the copper sulfate solution to form iron sulfate, while the copper deposits onto the iron surface.