reactions and chemical properties of the group 2 elements

reactivity of group 2 elements down the group

reactivity increases

are group 2 elements more or less reactive than group 1?

more

group 2 element + cold water

metal hydroxide + hydrogen

exception: magnesium as very unreactive

general observations of group 2 elements (except Mg) with cold water

- fizzing

- metal dissolves

- solution heats up

magnesium + steam/warm water

steam: magnesium oxide formed, burns with a bright white flame, MgO is a white powder

warm water: magnesium hydroxide formed, slow reaction, no flame

both reactions also produce hydrogen gas

group 2 element + oxygen

burn in oxygen to form metal oxides

solubility of group 2 metal hydroxides

Solubility increases down the group

what do all group 2 hydroxides appear as?

white precipitates

solubility of magnesium hydroxide in water

- classed as insoluble (sparingly soluble)

- a suspension of magnesium in water will be slightly alkaline (pH 9) meaning slight dissolving as OH- produced

solubility of calcium hydroxide in water

- partially soluble

- appears as white precipitate

how does the pH of a suspension of calcium hydroxide in water compare with the pH of a suspension of magnesium hydroxide in water

A suspension of calcium hydroxide in water will appear more alkaline (pH 11) than magnesium hydroxide as it is more soluble so there will be more hydroxide ions present in solution

solubility of barium hydroxide in water

- easily dissolve in water

- hydroxide ions present would make the solution strongly alkaline

solubility of group 2 metal sulfates

decreases down the group

barium sulfate least soluble

how to test for sulfate ions

Add dilute HCl and Barium chloride to form a white precipitate of barium sulfate

why is HCl needed in the test for sulfate ions?

- to react with carbon impurities which would from a white barium carbonate precipitate resulting in a false positive

- if carbonate ions present: fizzing due to carbon dioxide

why cant you use sulfuric acid to test for sulfate ions?

contains sulfate ions so would give false positive