Group 2 And 7 Flashcards
Atomic radius - 2
Increases
-NO. Principal energy levels increases
- Shielding increases
- less attraction between Valence e- and nucleus
First IE down group 2
Decreases
- NO. Principal E levels increases
- shielding increases
- weaker attraction between valence e- and nucleus
Melting point down group 2
Decreases
- size of ion increases
- weaker electrostatic forces of attraction between positive ions and delocalised e-
Group 2 + water reactivity down group
-More reactive down group
-atomic radius increases
- shielding increases
- reactivity increases
More vigorous, warmer, more ppt
Group 2 + water eqn
X + H2O -> X(OH)2 +H2
Mg with steam
Mg + H2O -> MgO + H2
s. g. s. g
White solid white flame
Solubility of group 2 hydroxides (not explanation)
Mg - very sparingly white ppt
Ca - sparingly White ppt
Sr - slightly
Ba - soluble
Group 2 hydroxides pH
Mg 8-9
Ca 10-11
Sr 11-12
Ba 13-14
More OH- ions in solution
Test for Mg 2+ ions in solution
(Sodium) hydroxide + solution with Mg2+
- white ppt of Mg(OH)2
MgCl2 + 2NaOH-> Mg(OH)2 + 2NaCl
Aq. Aq. S. Aq
Mg2+ + 2OH- -> Mg(OH)2
Aq. Aq. S
Test for OH- ions in solution (group 2)
Magnesium (chloride) solution + solution with OH-
White ppt of Mg(OH)2
MgCl2 + 2NaOH-> Mg(OH)2 + 2NaCl
Aq. Aq. S. Aq
Mg2+ + 2OH- -> Mg(OH)2
Aq. Aq. S
Test for Ba2+ ions in solution
Sulphuric acid + barium ions
White ppt
H2SO4 + BaCl2 -> BaSO4 + 2HCl
Aq. Aq. S. Aq
SO4 ²- + Ba2+ -> BaSO4
Aq. Aq. S
Test for SO4 ²- ions in solutions
ACIDIFIED barium (chloride) + sulfate ions
Na2SO4 + BaCl2 -> BaSO4 + 2NaCl
Aq. Aq. S. Aq
SO4 ²- + Ba2+ -> BaSO4
Aq. Aq. S
Why does barium chloride have to be acidified in a sulphate ion test
With HCl or HNO3
- Remove carbonate ions that would give false positive
2H+ + CO3 ²- -> CO2 + H2O
BaCO3 formed
Uses of Mg(OH)2
Neutralises, excess stomach acid
CaCO3 not used as produces CO2
Ca(OH)3 uses
Neutralises acidic soils
CaO & CaCO3 uses
Fluegas desulphurisation
Neutralises SO2
CaO + SO2 -> CaSO3
BaSO4 uses
CT scans/x-rays
Barium meal, damaged areas of digestive tract seen
Insoluble
BaCl2 uses
Test for sulphate in solutions
Ba²- + SO4²- -> BaSO4
Uses of Mg
Extraction of titanium
Process of titanium extraction
Rutile ore high temp
TiO2 + 2Cl2 + 2C -> TiCl4 + 2CO
S. G. S. G. G
Magnesium used as reducing agent heated, atmosphere of argon (inert)
TiCl4 + 2Mg -> Ti 2MgCl2
Halogens as oxidising agents
Down group, less oxidising
-Size increases
-more shielding
-Gain electrons, less readily
-weaker attraction from nucleus
Cl2 + 2NaBr
-> 2NaCl + Br2 (yellow)
Cl2 + 2NaI
-> 2NaCl + I2 (brown)