Group 2 Flashcards
Give the general formula for reacting a group 2 metal with water.
M (s) + 2H2O (l) -> M(OH)2 (aq) + H2
Give the formula for reacting magnesium with steam.
Mg (s) + H2O (g) -> MgO (aq) + H2 (g)
What sort of reaction does magnesium have with water?
Very slow, hence the reason for using steam.
Explain how the solubility of a group 2 hydroxide changes as we go down the group.
It increases. Mg(OH)2 is sparingly soluble; Ca(OH)2 slightly soluble forming a cloudy alkaline solution; Sr(OH)2 forming cloudy alkaline solution.
How are elements lower down the group stored and why?
In oil to prevent reaction with water in the air as they get more reactive as they go down the group and they get more exothermic.
Explain the trend in atomic radius as we go down group 2s.
It increases due to more electron shells being filled.
Explain the trend in hydroxide solubility as we go down group 2s.
It increases.
State and explain the trend in reactivity as we go down group 2s.
It increases due to atoms needing to lose one electron to form a stable outer shell. It is easier to do this due to a larger radius and more shielding of inner electrons, despite a larger nuclear charge.
State the trend in first ionisation energy as we go down the group.
With similar reasons to reactivity, the first ionisation energy decreases as we go down the group due to more shielding and larger atomic radius.
Explain the trend in melting points of group 2 metals.
It decreases generally, apart from magnesium where it goes down more than usual then goes back up a bit for calcium. The exception is due to magnesium having a different crystalline structure to the others. The general trend is due to an increased radius, so there is a lower charge density so it is easier to separate the ions and delocalised electrons.
Define solubility.
The amount of solute that will dissolve in a particular solvent.
Give three factors that influence solubility.
Volume of solvent;
Temperature of solvent;
Pressure (in gases).
State the general trend in group 2 hydroxide solubility.
It increases as we go down the group.
State the general trend in group 2 sulphate solubility as we go down the group.
It decreases as we go down the group.
Give 2 uses of magnesium hydroxide.
Antacid (neutralises excess stomach acid);
Reacts with HCl to produce MgCl (and water), a laxative.
