reacting with water

• trend in reactivity with water down group 2

  • increases
  • atomic radius increases
  • electron shielding increases
  • the outer electrons are more readily lost
  • therefore reactivity increases
• group 2 metals react with water to form metal hydroxides and hydrogen gas
• when group 2 and water react the group 2 element is oxidised and loses two electrons to form a 2+ ion
• the metal hydroxide solubility increases as you go down group 2
• Be does not react with water
• effervescence occurs when a group 2 metal reacts with water due to H being reduced
• Mg reacts slowly with liquid water to form a slight white precipitate
• Mg reacts faster with water in a gas state (steam) than in a liquid state
• equation for Mg reacting with water with state symbols

  Mg(s) + 2H20(l) ——> Mg(OH)2(s) + H2(g)
• equation for Mg reacting steam with state symbols

  Mg(s) + 2H20(g) ——> MgO(s) + H2(g)
• calcium reacts steadily with cold water
• when calcium reacts with water the solution goes cloudy as the hydroxide isn’t very soluble and forms a slight white precipitate
• equation for Ca reacting with water with state symbols

  Ca(s) + 2H2O(l) ——> Ca(OH)2(s) + H2(g)
• when calcium reacts with excess water a small amount of calcium hydroxide dissolves
• equation for excess water reacting with calcium hydroxide with state symbols

  Ca(OH)2 (s) ——> Ca2+(aq) + 2OH-(aq)
• Sr reacts vigorously with cold water to form a colourless solution
• equation for Sr reacting with water with state symbols

  Sr(s) + 2H2O(l) ——> Sr(OH)2(aq) + H2(g)
• Ba reacts vigorously with cold water to form a colourless solution
• equation for Ba reacting with water with state symbols

  Ba(s) + 2H2O(l) ——> Ba(OH)2(aq) + H2(g)