Group 2

• BaO + water

  UI = dark purple, pH around 13, much more soluble in water than Ca and Mg hydroxide
• CaO + water

  UI = purple, pH around 12, slightly soluble in water but more than Mg(OH)2
• MgO + water


  UI = dark green, pH around 10, slightly soluble in water, low conc of OH- ions
• Unsaturated hydroxide ions


  When more metal oxide is added, the solution becomes saturated as the resulting metal hydroxide doesn't dissolve anymore
• Group 2 oxide + water

  group 2 oxides react with water and release OH⁻ ions⚬ Group 2 oxide + water → metal ion + OH-⚬ e.g CaO + H₂O → Ca²⁺ + 2OH⁻The solution becomes saturated as oxides only slighty soluble in water. any further metal + OH⁻ ions form a precipitate⚬ Metal ion + OH → group 2 hydroxide⚬ Ca²⁺ + 2OH⁻ → Ca(OH)₂
• Solubility and pH of group 2 hydroxides

  The solution pH increases and hydroxide solubility increases, more hydroxide ions produced so pH becomes more alkaline, solubility increases down the group
• What happens as you go down group 2 in terms of reactions?


  The reactions become more vigorous
• Group 2 + Hydrochloric acid


  Metal chloride + hydrogen gas
• Group 2 + oxygen

  2M + O2 -> 2MO
• Group 2 + water

  metal hydroxide + hydrogen gas
• Reactivity trend in group 2

  Reactivity increases down the group: shielding increases, ionisation energy decreases and decreased nuclear attraction