Chapter 9 Group 2, the Alkaline Earth metals Flashcards
(12 cards)
what is the trend in atomic radius for group 2?
forms 2+ ions when they react
increases as we go down as there are extra electron shells
what is the trend in ionisation energy down group 2?
decreases
as there are extra shells, so more shielding hence weaker attraction between the nucleus and outer electrons -> further from nucleus so easier to remove
increase in protons but shielding effect overrides this
what is the trend in reactivity down group 2?
increased electron shielding down group makes outer electron easier to remove, therefore reactivity increases down the group
what is the trend in melting point down group 2?
they are metallic therefore the larger the ions within the metallic structure, the weaker the attractive forces thus decrease in melting point down the group
what occurs when group 2 reacts with water?
produces a metal hydroxide and hydrogen, these metal hydroxides form as an alkali soluton
e.g: Mg (s) + 2H2O (l) -> Mg(OH)2 + H2
atom gets larger therefore electrons further from nucleus, easier to remove and hence more reactive
what is the exception for the reaction with water in group 2?
magnesium reacts very slowly in liquid water, however it reacts much faster with steam. when steam is used magnesium burns in a bright white flame to form hydrogen and magnesium oxide (white powder)
what is the solubility of the hydroxides down group 2?
will increase down the group meaning magnesium hydroxide (Mg(OH)2) is the least soluble, and barium hydroxide (Ba(OH)2) is the most soluble.
as a result magnesium hydroxide can be used in medicine as an antacid to neutralise stomach acid
what is the solubility of sulfates down group 2?
decreases, meaning magnesium sulfate (MgSO4) is the most soluble and barium sulfate (BaSO4) is the least soluble
therefore barium is useful in medicine such as barium meals and allows internal tissues and organs to be imaged. insoluble therefore will not be absorbed into the bloodstream
how do you test for sulfate ions?
barium chloride
1. add hydrochloric acid acid to remove any carbonates
2. add barium chloride
white precipitate forms if sulfate ions are present, white precipitate will be barium sulfate as it is insoluble
how is titanium extracted?
- titanium ore is converted to titanium(IV) chloride by heating with carbon and chlorine gas
- titanium(IV) chloride is passed through a fractional distillation column to increase purity
- TiCl4 is reduced using magnesium
TiCl4 + 2Mg -> Ti + 2MgCl2
how is sulfur dioxide removed?
wet scrubbing
- an alkali is used to neutralise the sulphur dioxide in flue gases
1. dissolving calcium carbonate or oxide in water and spraying on acidic sulphur dioxide gas
calcium carbonate:
CaCO3 + 2H2O + SO2 -> CaSO3 + 2H2O + CO2
oxide in water:
CaO + 2H2O + SO2 -> CaSO3 + 2H2O
what is calcium sulfite used for from the removal of sulphur dioxide gas?
production of plasterboard
