Group 2

• What is the general trend in atom size?

  Increases down the group, there are more electron energy levels.
• What is the general trend in melting point?

  Decreases down the group, metallic bonding gets weaker as the sea of delocalised electrons are further from the positive nuclei.
• What is the general trend in 1st ionisation energies?

  Decreases down the group. Outer electron is further and more shielded from the nucleus so also more reactive.
• What is the general trend in reactivity?

  Increases down the group. Easier to lose outer most electron because of shielding and distance from the nucleus.
• When elements of group 2 re oxidised what charge ions do they make.

  2+

  $Mg\ \rightarrow\ Mg^{2+}$
• What is the equation for the reaction of Mg with water?

  $Mg\ +$$2H2O\ \rightarrow\ Mg\left(OH\right)2\ +$$H2$
• What are the observations of the reaction of Mg +H2O?

  White precipitate

  Bubbles of hydrogen gas (very slow reaction)
• What is the common name for Mg(OH)2?

  Milk of Magnesia
• What is milk of Magnesia used for?

  An indigestion remedy
• How does milk of magnesia work?

  It is an alkali so neutralises stomach acid
• What is the equation for the reaction of Ca and water?

  $Ca\ +$$\ 2H2O\ \rightarrow\ Ca\left(OH\right)2\ +$$H2$
• What are the observations of the reaction of Ca +H20?

  Slight misty white precipitate

  See Bubbles of hydrogen gas (reacts faster)
• What are the used of Ca(OH)2 and CaO?

  Used to line power station chimney's because they neutralise acid rain gases. e.g. SO2
• Does solubility of hydroxides increase or decrease down the group?

  Increases down the group

  Mg(OH)2 -> insoluble

  Ca(OH)2 -> sparingly soluble

  Sr(OH)2 -> quite soluble

  Ba(OH)2 -> soluble
• Does solubility of sulfates increase or decrease down the group?

  Decrease down the group

  MgSO4 -> aqueous, colourless solution

  CaSO4

  SrSO4

  BaSO4 -> solid, thick white precipitate
• What do we know about BaSO4 that we use when testing for sulfate ions?

  BaSO4 is insoluble
• How do you test for sulfate ions?

  • Add dilute acid (HCl). Thsi will react and remove any carbonate impurities, which stops BaCO3 precipitate being misidentified as a sulfate
  • Add a few drops of BaCl2 (aq)
  • See a thick white precipitate form
• What is the equation for the test for sulfate ions?

  $Na2SO4\ +$$\ BaCl2\ \rightarrow\ BaSO4\ +$$2NaCl$

  Ionic equation: $SO4^{2-}+$$Ba^{2+}\rightarrow\ BaSO4$
• Why can you use BaSO4 in a barium meal even though it is toxic?

  It is insoluble so you can swallow it because it does not get absorbed into the body.
• Why is BaSO4 good at finding blockages (ect) through the digestive system?

  Good at absorbing x-rays, so you can see it travelling through the digestive system and find where the blockages are.
• What can Mg be used for?

  Extracting Titanium from titanium chloride (TiCl4)
• What is the equation for titanium IV oxide and chlorine and carbon?

  $TiO2\ +$$2Cl2\ +$$C\ \rightarrow\ TiCl4\ +$$2CO$
• What is the displacement reaction for TiCl4 and magnesium?

  $TiCl4\ +$$2Mg\ \rightarrow\ 2MgCl2\ +$$Ti$
• Why is extracting expensive?

  Mg is extracted by electrolysis which require large amounts of energy and therefore has a large energy cost, making it expensive