Inorganic Chemistry Flashcards
Groups 1 and 2
All have the highest energy electron in the s subshell
Group 2 reacting with O2
- except Be, they all react vigorously, producing a bright flame
- 2M + O2 -> 2MO
- Ba + O2 -> 2BaO2
- contains a peroxide ion
Peroxide ion
(O2)2-
2Mg + O2 -> 2MgO
- bright white flame
* used in fireworks and flames
Ca + Sr with O2
red flames
Ba + O2 -> 2BaO2
Green flame
Group 2 reactions with water
- less reactive than the corresponding group 1 elements
- Be does not react with steam
- Mg reacts v. slowly w/ cold water and does react w/ steam
- Ca, Sr and Ba all react w/ cold water with increasing vigour
Mg (s) + H2O (g)
-> MgO(s) + H2 (g)
Ca (s) + 2H2O
-> Ca(OH)2 + H2(g)
Calcium hydroxide is only sparingly soluble in water, so a thick white suspension accompanies the effervescence
Sr(s) + 2H2O (l)
-> Sr(OH)2 + H2 (g)
Strontium hydroxide is slightly soluble in water
Ba(s) + 2H2O (l)
-> Ba(OH)2 + H2 (g)
Barium hydroxide is soluble in water
Group 2 reactions with chlorine
All form chlorides
Group 2 oxide reacting with water
- BeO is not attacked by water
* others are ionic; react to form hydroxides
Group 2 oxides reacting with dilute acids
All produce salt and water
Group 2 hydroxides (bases)
React with acids in neutralisation to form salt and water
Group 2 sulphate solubility
Solubility decreases down the group
MgSO4 -> soluble
CaSO4 -> slightly soluble
SrSO4 -> insoluble
BaSO4 -> insoluble
Testing for sulphate ions
- used because BaSO4 is highly insoluble
- if BaCl2 is added to a solution containing sulphate ions, a white ppt is produced
Ba2+(aq) + (SO4)2-(aq) -> BaSO4(s)
Group 2 hydroxide solubility
- solubility increases down the group
- Ca(OH)2 is not very soluble in water; much more soluble than CaCO3
- when CO2 is passed through Ca(OH)2, it forms insoluble CaCO3 suspension, turning limewater cloudy
Indicator of carbonate thermal stability
Time taken for gas evolved to turn limewater cloudy
All group 1 carbonates are…
… thermally stable up to Bunsen temperatures; smaller charge density; lower polarising power
Lithium and group 2 carbonates thermally decompose to form
Metal oxide + CO2
Stability trend down Group 2
- more stable
- charge density decreases
- smaller polarising power
- cannot draw oxygen towards it as easily
- does not distort the C-O bond to the same extent
- need more vibrational energy as the bond has not been as weakened
- harder to release the CO2 and form the metal oxide