Group 2

• Explain why the melting point of calcium sulfate is high.  (2)


  • Strong attraction 
  • Between positive and negative ions
• State the trend in solubility, in water, of the Group 2 sulfates from magnesium to barium.


  decreases
• Write an equation for the reaction of calcium with water at 25 °C and predict a possible value for the pH of the solution formed.


  • Ca + 2H2O ⟶ Ca(OH)2 + H2 
  • 8 − 12
• Strontium metal can be extracted by heating strontium oxide with aluminium metal. In this reaction, strontium vapour and solid aluminium oxide are formed. Write an equation for the reaction and state the role of the aluminium in the process. Explain why strontium forms a vapour but aluminium oxide is formed as a solid.


  • 3SrO + 2Al ⟶ Al2O3 + 3Sr 
  • Al acts as a reducing agent 
  • Sr is collected as a vapour because 
  • Al2O3 is an ionic lattice and so has strong ionic attractions 
  • Than Sr which is a metallic structure with (relatively) weaker bonding 
• Describe how a student could distinguish between aqueous solutions of magnesium chloride, MgCl2, and aluminium chloride, AlCl3, using one simple test-tube reaction. 


  • Reagent: NaOH / sodium hydroxide
  • Observation with MgCl2(aq): white precipitate
  • Observation with AlCl3(aq): (white) ppt which dissolves in excess (NaOH) 
• Describe how a student could distinguish between aqueous solutions of potassium nitrate, KNO3, and potassium sulfate, K2SO4, using one simple test-tube reaction. (3)


  • BaCl2 / Ba(OH)2 / Ba(NO3)2  (reagent)
  • Observation with KNO3(aq): colourless solution
  • Observation with K2SO4(aq): white precipitate
• Which products are formed when magnesium reacts with steam? 


   Magnesium oxide and hydrogen 
• Ionic equation for barium chloride with sodium sulfate 

  Ba(2+) + SO4(2–) → BaSO4
• Give the formula of the hydroxide of the element in Group 2, from Mg to Ba, that is least soluble in water.


  Mg(OH)2
• Identify the s-block metal that has the highest first ionisation energy


  Be
• Explain why the second ionisation energy of calcium is lower than the second ionisation energy of potassium. (2)


  •  In Ca(+) (outer) electron(s) is further from nucleus 
  •   More shielding (in Ca+)
• What is Mg(OH)2 used for 


  treat symptoms of indigestion
• What is used to extract Ti


  Magnesium
• What is the correct observation when barium metal is added to an excess of water? 


  Forms a colourless solution and effervesces
• Give an equation for the reaction between titanium(IV) chloride and magnesium. State the role of magnesium in this reaction. 


  • 2 Mg + TiCl4 → Ti + 2 MgCl2 
  • Role: Reducing agent
• State what is observed when dilute aqueous sodium hydroxide is added to separate solutions of magnesium chloride and barium chloride. 


  • Observation with MgCl2: white ppt
  • Observation with BaCl2: no (visible) change / colourless solution / no reaction
• What is titanium naturally found as 

  TiCl4
• Give an equation to show how magnesium is used as the reducing agent in the extraction of titanium. 

   2Mg + TiCl4 → 2MgCl2 + Ti
• What is Ca(OH)2 used for 


  • slaked lime
  • neutralises acidic soil
• Barium is toxic but safe to inegest. Why?


  • insoluble 
• What is BaSO4 used for 


  • barium meal 
  • used in x-rays 
• Explain why the melting point of magnesium is higher than the melting point of sodium. (2)

  • Mg2+ has a higher charge than Na+ / Mg2+ ions are smaller / Mg2+ has a greater charge density / Mg atoms smaller than Na atoms / Mg has more delocalised electrons than Na
  • Stronger attraction to delocalised sea of electrons / stronger metallic bonding 
• give one medical use for magnesium hydroxide.


  • Idigestion relief / laxative / neutralise (excess stomach) acid 
• Explain, in terms of structure and bonding, why magnesium chloride has a high melting point. (3)

  • (Giant) ionic lattice / lots of Mg2+ and Cl– ions 
  • Strong (electrostatic) forces of attraction 
  • Between Mg2+ and Cl– ions 
• Describe the bonding in magnesium. (2)

  • Attraction between (lattice of) Mg2+ ions 
  • And delocalised electrons 
•  State one observation when magnesium reacts with steam. 


  white light
• What are antacids 


  Indigestion tablets 
• What is the trend with SO42- down G2


  Less soluble 
• What is the trend with OH- down G2


  More soluble 
• Mg with steam 


  steam

  
• Mg with cold water 


  cold water

  
• What are G2 known as 


  Alkaline earth metals