Periodicity And Group 2

Question 1

Trend of melting points across period 3

Answer 1

Melting points of metallic elements increase
Melting point of silicon is highest
Melting points of non metals are low

Question 2

What are trends down group 2

Answer 2

Atomic radius increases- more shielding
Decreased ionisation energy- atomic radius increases more shielded
Melting points decrease- metallic bond weaker as ions get bigger with same number of delocalised electrons

Question 3

Reactions of group 2 metals with water

Answer 3

Be- no reaction
Mg- very slow (mg(oh)2), rapid with steam (mgo)
Reactivity increases down the group

Question 4

Solubility of group 2 hydroxides

Answer 4

Solubility increases down the group
Found by adding NaOH and observing precipitate

Question 5

Solubility of group 2 sulfates

Answer 5

Become less soluble down the group
Found by adding Na2SO4 and observing the precipitate

Question 6

Test for sulfate

Answer 6

Add dilute HCl
Add BaCl
Positive result- white precipitate
Ba2+(aq) + SO4 2-(aq) -> BaSO4 (s)

Question 8

Uses of magnesium compounds

Answer 8

Extract titanium
Titanium-corrosion resistant, strong but lightweight
TiCl4 + 2Mg -> Ti + 2MgCl2
Mg(OH)2 -> antacid to neutralise excess acid in the gut

Question 9

What are uses of calcium compounds

Answer 9

Ca(OH)2- neutralise acidic soil
CaO- neutralise SO2, a byproduct of combustion of fossil fuels, to prevent acid rain forming
CaCO3- neutralise SO2

Question 10

Uses of barium compounds

Answer 10

BaSO4- eaten as part of a barium meal to be taken before xrays. Allows outline of gut to be pictured
Harmless due to its insoluble properties