Group 2 Flashcards
(15 cards)
What is the trend in melting points down group 2?
Decreasing
Give the equation for a group 2 metal reacting with oxygen
2M(s) + O₂(g) → 2MO(s)
Give the equation for a group 2 metal reacting with water
M(s) + H₂O(l) → M(OH)₂(aq) + H₂(g)
What is the trend in reactivity with water going down group 2?
Increasingly vigorous
Mg only reacts with warm water
What observations can be made when a group 2 metal reacts with water?
Steam - exothermic
Effervescence
White precipitate (Mg and Ca only)
Give the equation for a group 2 metal reacting with steam
M(s) + H₂O(g) → MO(s) + H₂(g)
Why must Ti be extracted with Mg?
Cannot be reduced with carbon - forms TiC
Must be pure so cannot use electrolysis
Give the equations for extracting pure Ti from TiO₂
TiO₂ + 2Cl₂ → TiCl₄ + 2CO
TiCl₄ + 2Mg → Ti + 2MgCl₂
How is Ti extracted from TiO₂?
Reacted with C and Cl₂ to form TiCl₄
TiCl₄ purified by fractional distillation in argon
TiCl₄ reacted with Mg in argon at 500°C
Why is extraction of Ti expensive?
Mg is expensive
Multiple steps required
High cost of heating reaction vessel to 500°C - vessel must be cooled between batches
What is the trend of solubility of hydroxides moving down group 2?
Increasing
Mg produces a white precipitate if NaOH is added to a soluble salt e.g. MgCl₂(aq)
Give three uses of group 2 metal hydroxides
Mg(OH)₂ used to treat indigestion / constipation (milk of magnesia)
Ca(OH)₂ used to neutralise acidic soils
Ca(OH)₂(aq) used to test for presence of CO₂
Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l)
What is the trend of solubility of sulfates moving down group 2?
Decreasing
Give a use of a group 2 metal sulfate
BaSO₄ used for x-rays of intestines as it absorbs x-rays
Not toxic as insoluble so doesn’t enter blood
What is the test for sulfate ions?
Add acidified BaCl₂, white precipitate forms if present
Acidified to prevent carbonate ions giving false positive
