group 2 Flashcards
in all of their reactions, the group 2 metals are
oxidised
what does oil rig stand for
● oxidation (inc in OS) is loss (of e-)
● reduction (dec in OS) is gain (of e-)
explain oxidation states
● simplify processes of what’s being oxidised and what’s being reduced in redox reactions
● oxidation involves inc in os
● reduction involves dec in os
what are the rules of oxidation states?
● oxidation of an uncombined element is 0
● sum of oxidation states of all atoms or ions in a neutral compound is 0
what is the usual oxidation state of a group 1 metal?
+1
what is the usual oxidation state of a group 2 metal?
+2
what is the usual oxidation state of oxygen?
-2
what is the usual oxidation state of hydrogen?
+1
what is the usual oxidation state of fluorine and chlorine?
-1
what happens when group 2 metals react with water?
● metal is oxidised
● hydrogen is reduced
what are the observations of group 2 metals (alkali earth metals) reacting with water?
● Be:
observations: unreactive with water and steam
equation: X
● Mg:
observation: very slow reaction with water, faster with steam
equation: water: Mg(s) + 2H2O(l) -> Mg(OH)2(aq) + H2(g)
steam: Mg(s) + H2O(g) -> MgO(s) + H2(g)
● Ca:
observation: fizzing / effervescence when in cold water
equation: Ca(s) + 2H2O(l) -> Ca(OH)2(s) + H2(g)
● Sr:
observation: reacts vigorously with cold water
equation: Sr(s) + 2H2O(l) -> Sr(OH)2(s) + H2(g)
● Ba:
observation: reacts more vigorously with cold water
equation: Ba(s) + 2H2O(l) -> Ba(OH)2(aq) + H2(g)
what is the solubility of group 2 hydroxides?
● formed when group 2 reacts with water
● Mg(OH)2:
insoluble
equation: Mg(OH)2(s) -> almost insoluble
● Ca(OH)2:
slightly soluble
equation: Ca(OH)2 (s) -> Ca2+ (aq) +2OH-(aq)
● Sr(OH)2:
soluble
equation: Sr(OH)2 (s) -> Sr2+ (aq) + 2OH-(aq)
● Ba(OH)2:
soluble
equation: Ba(OH)2(s) -> Ba2+ (aq) + 2OH-(aq)
● solubility increases down group 2 hydroxides
● white - colourless as you go down group
what is the solubility of group 2 sulfates?
● made when group 2 metal reacts with sulfate ions (e.g. sulphuric acid)
● MgSO4:
soluble
equation: x
colourless
● CaSO4:
slightly soluble
equation: Ca2+ (aq) + SO42-(aq) -> CaSO4 (s)
cloudy
● SrSO4
insoluble
equation: Sr2+ (aq) + SO42- (aq) -> SrSO4(s)
white precipitate
● BaSO4
insoluble
equation: Ba2+ (aq) + SO42- (aq) -> BaSO4(s)
white precipitate
● solubility of group 2 sulfates decreases down group
explain extraction of Ti
● strong, low density, high melting point
● used in aerospace industry and replacement hip joints
● abundant but difficult to extract
● metals are typically extracted by:
metal oxide + carbon -> metal + carbon dioxide
● however, method produces titanium carbide which is very brittle so different method must be used
● 1. titanium oxide is reacted with chlorine and carbon
TiO2 + 2Cl2 + 2C -> TiCl4 + 2CO
● 2. titanium chloride is reduced using magnesium
TiCl4 + 2Mg -> 2MgCl2 + Ti
explain milk of magnesia
● Mg(OH)2
● indigestion remedy
● neutralises excess stomach acid
