Group 2

• Why does the melting point decrease as you go down group 2?

  • Atomic radius increases
  • Lower charge density
  • Weaker attraction between positive metal ions and delocalised electrons
• Why are elements of group 2 classified as S block elements?

  Their valance electron is in the S orbital
• State and explain the trend in atomic radius as group 2 descends

  • Atomic radius increases as there are more electron shells
• Why does the first ionisation energy from Mg to Ba decrease?

  • The atomic radius increases as you go to Ba from Mg, due to this there are weaker forces of attraction between the valance electron and the protons in Ba so the valance electron can be lost easier.
• Why does the melting point decrease as you go down group 2?

  • As you could go down group the atomic radius increases.
  • This results in weaker attraction between positive metal ions and delocalised electrons.
• What is the trend in ease of reactivity as you go down the group?

  • It increases
• Write the equations for Mg reacting with steam and water.

  • Steam : Mg(s) + H2O(g) --> MgO(s) + H2(g)
  • Water : Mg(s) + 2H2O(l) --> Mg(OH)2(s) + H2(g)
• Why is there a difference in the reactions between magnesium + steam and magnesium + water?

  • Magnesium, reacts slowly in water, but quickly with steam
• What is the observation when Mg, Ca, Sr and Ba react with water?

  • Mg - bright glow.
  • Ca - Bubble and fizz, white precipitate.
  • Sr - Bubbles and fizzes more vigorously.
  • Ba - Bubbles and fizzes vigorously.
• What is the trending solubility of group 2 hydroxides as you go down the group?

  • The solubility increases.
• What is the solubility trend for group 2 sulphates? As you go down the group.

  • The solubility decreases
• What is the ionic equation for the formation of BaSO4?

  • Ba^2+ (aq) + SO4^2- (aq) --> BaSO4 (s)
• What is the use of Mg(OH)2?

  • Antacid - neutralises excess stomach acid
• What is the use of Ca(OH)2?

  • Slaked-lime; neutralises acidic soil
• What is the use of BaSO4?

  • Barium meal - X-rays
• If XSO4 or X(OH)2 is formed what is the observation?

  • A white precipitate is formed
• Why can BaSO4 be used in medicine and to test for SO4^2- ions?

  • It is completely insoluble in water
• What's the method for testing for SO4^2- ions?

  • Add equal amounts of hydrochloric acid to the sample
  • Add BaCl2 to the sample, if a white precipitate is formed SO4^2- ions are present.
• Why do we add hydrochloric acid when testing for SO4^2- ions?

  • It removes impurities like carbonate ion from the sample which can give false positive results

  o Ba^2+ (aq) + CO3^2- (aq) --> BaCO3 (s)

  • Removal equation - 2H+ (aq) + CO3^2- (aq) --> H2O (l) + CO2 (g)
• Why can you not use sulphuric acid over hydrochloric acid when testing for SO4^2- ions?

  • Sulphuric acid already contains sulphate ions, so we wouldn't know if the original solution contained sulphate ions in the first place.
• Why can't titanium be extracted in the usual way?

  Metal oxide + carbon --> metal + CO2

  • TiC is formed instead
  • It's extremely brittle and of very little use.
• What are the 2 steps that titanium extraction occurs in and include conditions needed to achieve this?

  • The ore of titanium, TiO2, is converted to TiCl at 900°C
  • TiO2 (s) + 2Cl2 (g) + 2C (s) --> TiCl4 (l) + CO2
  • The titanium is extracted from TiCl4 by reacting it with magnesium in an argon atmosphere at 1000°C
  • TiCl4 + 2Mg --> Ti + 2MgCl2
• Why do we use an argon atmosphere in the extraction of titanium?

  • Argon provides an inert atmosphere, preventing magnesium from reacting with oxygen
• What are the two ways that flue-gas desulphurisation can be carried out? Include the equations used

  • If Calcium oxide, CaO, is used it is hydrated by SO2 to make hydrated calcium sulphate
  • CaO (s) + 2H2O (l) + SO2 (g) + ½O2 (g) --> CaSO4.2H2O
  • If calcium carbonate, CaCO3 is used it produces calcium sulphate and CO2
  • CaCO3 (s) + ½O2 (g) + SO2 (g) --> CaSO4 (s) + CO2 (g)