group 2 key equations

Question 1

reactions with metal and oxygen
what is the observation with magnesium?

Answer 1

metal + oxygen —> metal oxide
Mg burns with bright white flame

Question 2

reactions with water

Answer 2

metal + water —> metal hydroxide + hydrogen
-exception: mg reacts differently in steam
Mg (s) + H2) (g) —> MgO (s) + H2 (g)
observations: bright white flame and produces a white precipitate

Question 3

using mg to extract titanium
1. titanium from a solid to liquid
2. titanium extracted by magnesium
3. advantages + disadvantages of extracting titanium

Answer 3

1. TiO2 solid –> TiCl4 liquid (900 oc)
   TiO2 + 2Cl2 + 2C —> TiCl4 + 2CO
2. TiCL4 purified by fractional distillation
3. Ti extracted by Mg (500 oc)
   TiCl4 + 2Mg —>Ti + 2MgCl2

titanium is abundant but extraction is expensive due to batch process and high temperatures

Question 4

solubility of hydroxide trend
what is the purpose of mg(oh)2 and ca(oh)2?
what does the insoluble form?

Answer 4

-more soluble down a group (OH-)
-insoluble: white precipitate
use of hydroxides: Mg(OH)2 is used to neutralise stomach acid
-Ca(OH)2 is used to neutralise soil

Question 5

solubility of sulfates

Answer 5

-less soluble down group
(SO2- 4)
-insoluble: white precipitate

Question 6

ionic equation of barium ions

Answer 6

Ba2+ (aq) + SO42- (aq) —> BaSO4 (S)

Question 7

use of sulfates

Answer 7

BaSO4 is a barium meal, it is given to patients before xrays as barium absorbs xrays. Barium is toxic but safe as insoluble so not absorbed in blood

Question 8

testing for sulfates

Answer 8

1. add BaCl2 with HCl - Hcl rather than H2SO4 so no false positive
2. if white precipitate forms sulfate present
   -acid is needed to react with carbonate impurities
   acid + metal carbonate –> salt + water +CO2