Group 2

Question 1

Explain the trend in atomic radius from Be to Ba

Answer 1

Increases down the group because number of electrons increases.

Question 2

Explain the trend in 1st ionisation energies from Be to Ba

Answer 2

General decrease down the group
Outer electrons are higher in energy levels and further from the nucleus
Extra inner shells increase shielding from the increased nuclear charge
So the attraction by the nucleus decreases
Therefore less energy is needed to remove the outer electron

Question 3

Explain the trend in melting points from Be to Ba

Answer 3

General decrease down the group
As ion size increases, charge density decreases which reduces the attraction to the delocalised electrons
So the strength of the metallic bond decreases
The anomaly at Mg (lower melting point than Ca) is due to it having a different metallic structure to Ca

Question 4

Reactions with cold water (general equation)

Answer 4

M(s) + 2H2O(l) —> M(OH)2(aq) + H2(g)

Question 5

Which element can be reacted with steam to make its oxide?

Answer 5

Magnesium

Mg(s) + H2O(g) —> MgO(s) + H2(g)

Question 6

Extraction of titanium

Answer 6

Using carbon would produce impure titanium (titanium carbide impurities) which makes it more brittle.
So a more expensive displacement reaction with magnesium and titanium chloride in an argon atmosphere is used

TiCl4(l) + 2Mg(l) —> Ti(s) + 2MgCl2(l)

Question 7

Uses of magnesium

Answer 7

Extraction of titanium

Milk of magnesia (Mg(OH)2) for indigestion

Question 8

Use of Ca(OH)2 (Lime)

Answer 8

To treat soil (wheat, corn, oats and barley all grow better in soil with pH6)

Question 9

Neutralising SO2

Answer 9

Burning fossil fuels releases acidic SO2 gas
This can be neutralised by calcium oxide or calcium carbonate, which is sprayed onto the flue gases producing calcium sulphate (IV)

CaO + SO2 —> CaSO3
CaCO3 + SO2 —> CaSO3 + CO2