Group 2 The Alkaline Earth Metals Flashcards
What is the trend in atomic radius for group 2 + why
As you move down the group the atomic radius increases
Increased number of shells
What in the trend of ionisation energies in group 2 + why
Decreases as you move down group 2
There are more shells so further away from the positive nucleus this decreases attraction so less energy to remove outermost electron
General tend in melting point of group 2
Decreases as you move down group
Why does the melting point decrease as you move down group 2?
Metallic structure —-> positive metal ion and sea of delocalised electrons
As you move down size of atomic radius increases but number of delocalised electrons and charges are the same
Larger distance positive nuclei of metal ion and electrons
Weakens force of attraction less energy to break
When group 2 metals react with water are they oxidised or reduced
Oxidised
Trend in reactivity of group 2 with water + why
Increases moving down group
Larger atomic radius decreased ionisation energy less energy to lose the outer 2 electrons
Group 2 metal + water =
Metal hydroxide + hydrogen
General formula of group 2 metal + water
X(s) + 2H2O (l) —> X(OH)2 (aq) + H2 (g)
Must be balanced with state symbols
Magnesium + water vs magnesium + steam
Mg (s) + 2H2O (l) —-> Mg(OH)2 (aq) + H2 (g)
VS
Mg (s) + H2O (g) —> MgO (aq) +H2 (g)
Rate of reaction with water group 2 trend
Increases moving down group 2
How is titanium extracted
1) Titanium ore TiO2 is converted to Titanium chloride TiCl4 by heating with carbon and chlorine gas
2) pass TiCl4 through fractional distillation column to purify
3) purified TiCl4 is reduced using magnesium in 1000 degrees furnace
Equation for reduction of titanium chloride with magnesium
TiCl4 + 2Mg —-> Ti + 2MgCl2
Solubility of group 2 hydroxides trend
Increases going down the group
Solubility of group 2 sulphates trend
Decreases moving down the group
Uses of Mg(OH)2
Used for indigestion tablets because it neutralises stomach acids. AKA it’s a antacid
How soluble is Mg(OH)2
Sparingly
Uses of Ca(OH)2
Used in agriculture to neutralise acidic soils
How do you remove sulphur dioxide from flue gases
Web scrubbing
Alkali used to neutralise SO2 in flue gases
1) dissolve CaO or CaCO3 in water
2) spray on sulphur dioxide gas
Equation for web scrubbing
CaO(s) + 2H2O (l) + SO2 (g) —> CaSO3(s) + 2H2O (l)
CaCO3 (s) + 2H2O (l) + SO2 (g) —-> CaSO3 (s) + 2H2O (l) + CO2 (g)
Solubility of group 2 sulfates
Decreases going down group 2
Test for sulphate ions
1) add hydrochloric or nitric acid
2) add barium chloride
White precipitate - positive
Nothing - negative
Why do we need to add hydrochloric acid or nitric acid first for sulfates ion test
To remove carbonate ions ( by reacting to produce CO2)
Otherwise barium carbonate will form which is a white precipitate which is false positive
Uses of Barium sulphate in medicine
It is insoluble so does not enter blood stream
Patient give BaSO4 to eat because it absorbs X-rays. Dr can see digestive system
Ionic equation barium chloride + solution with sulfate ions
Ba+2 (aq) + SO4 2- (aq) —> BaSO4
Two difference reaction of magnesium with water and reaction magnesium with steam x3
Slower water vs faster steam
Magnesium hydroxide vs magnesium oxide
Bubbling of water vs bright white light
Reaction magnesium and calcium with sulfate
Magnesium sulfate soluble and calcium sulfate insoluble
Calcium sulfate coast the surface of the calcium
Coating prevents further contact with acid etc
Define rate of reaction
Amount of substance formed in unit time
Why does doubling reactant increases rate of reaction
Twice as many particles
Twice as many successful collisions
