Group 2

Question 1

Colour of group 2 metals flame when burnt in oxygen

Answer 1

Be - white
Mg - intense white
Ca - brick red
Sr - crimson
Ba - pale green

Question 2

Describe reaction of Be with steam

Answer 2

Reacts with steam at high temperatures to give white BeO and hydrogen

Question 3

Describe reaction of Mg with steam

Answer 3

Burns in steam to produce white MgO and H2 gas

Question 4

Describe reaction of Ca with water

Answer 4

Reacts fairly vigorously with cold water. White ppt of the hydroxide is produced

Question 5

Describe reaction of Sr and Ba with water and steam

Answer 5

Water: reacts vigorously to produce some white ppt.
Steam: burns explosively to form the oxide and hydrogen

Question 6

Describe reaction of Ca, Sr and Ba with sulfuric acid

Answer 6

A layer of insoluble sulfate forms on all these metals after they start reacting which will slow down the reaction or stop it entirely

Question 7

General equation for decomposition of nitrates, description and thermal stability trend

Answer 7

2M(NO3)2 —–> 2XO + 4NO2 + O2
Brown nitrogen gas is given off
The nitrates become more stable to heat

Question 8

General equation for decomposition of carbonates and trend in thermal stabilty

Answer 8

MCO3 —-> MO + CO2
They become more stable to heat down the group

Question 9

Explain the increase in thermal stability of nitrates and carbonates

Answer 9

Down the group, cationic radius increases, thus charge density decreases. The polarising power of the cations decreases down the group, the is less distortion of the electron cloud on the anion.

Question 10

Solubility of Mg, Ca and Ba sulfates

Answer 10

MgSO4 - soluble
CaSO4 - sparingly soluble
BaSO4 - insoluble

Question 11

Explain the solubility of group 2 sulfates

Answer 11

Due to an increase in cationic radii, both delta H latt and delta H hyd decrease. However, the magnitude of delta H hyd decreases more rapidly than that of delta H latt due to large size of anion. Hence delta H soln becomes less exothermic down the group

Question 12

Solubility of Mg, Ca and Ba hydroxides

Answer 12

Mg(OH)2 - insoluble
Ca(OH)2 - slightly soluble
Ba(OH)2 - soluble

Question 13

Explain the solubility of group 2 hydroxides

Answer 13

Due to an increase in cationic radii, both delta H latt and delta H hyd decrease. However, the magnitude of delta H latt decreases more rapidly than that of delta H hyd due to small size of anion. Hence delta H soln becomes more exothermic down the group

Question 14

Formula for delta H solution

Answer 14

Delta H solution = -delta H lattice energy + delta H hydration