Group 2

Which reaction shows the strong heating of magnesium nitrate?

• Mg(NO₃)₂ --> Mg(NO₂)₂ + O₂

• Mg(NO₃)₂ -->MgO₂ + 2NO₂

• Mg(NO₃)₂ --> MgO + N₂O + 2O₂

• 2Mg(NO₃)₂ --> 2MgO + 4NO₂ + O₂

The table shows the decomposition temperature of the carbonates of Group 2 elements.

Why is BeCO₃ unstable thermally?

• The electron cloud of the Be²⁺ ion is polarised by the CO₃^2– ion.

• The electron cloud of the CO₃^2– ion is polarised by the Be²⁺ ion.

• Going down Group 2, the size of the cation increases and the polarisation of the anion by the cation becomes greater.

• A small cation absorbs energy more efficiently and can be excited to a higher energy level which is unstable.

Magnesium is a Group 2 element. When magnesium carbonate is heated, magnesium oxide is formed and carbon dioxide is liberated.

MgCO₃ --> MgO + CO₂

Which of the following is true when going down the group?

• Lattice energy of carbonates decreases

  Lattice energy of oxides decreases

  Thermal stabilities of oxide decreases

• Lattice energy of carbonates decreases

  Lattice energy of oxides decreases

  Thermal stabilities of oxide increases

• Lattice energy of carbonates increases

  Lattice energy of oxides increases

  Thermal stabilities of oxide decreases

• Lattice energy of carbonates decreases

  Lattice energy of oxides increases

  Thermal stabilities of oxide decreases

A solution of aluminium nitrate will turn blue litmus paper to red because

• the Al³⁺ ion is hydrolysed

• the Al³⁺ ion has a high charge

• all aluminium compounds are acidic

• aluminium nitrate is an ionic compound

Beryllium is a Group 2 element. Which of the following is the anomalous properties of beryllium?

• Beryllium oxide is amphoteric

• Beryllium chloride does not dissolve in water

• Beryllium forms a covalent compound with fluorine

• Beryllium oxide can form dimer.

Aqueous beryllium chloride has a pH less than 7 because

• the charge density of the beryllium ion is high

• the beryllium ion undergoes hydrolysis

• beryllium chloride undergoes partial dissociation in water

• beryllium chloride is a covalent compound

The solubilities of the sulphates of Group 2 metals decrease down the group because

• the cation size increases from Mg²⁺ to Ba²⁺

• the hydration energy of the cations becomes less exothermic from Mg²⁺ to Ba²⁺

• the sulphates ion very much smaller than these cations.

The carbonates, nitrates and hydroxides of Group 2 elements decompose to their respective oxides when heated. Hence, it can be concluded that

• all compounds of Group 2 elements are unstable to heat

• Group 2 elements are strong reducing agents

• the oxide is energetically more stable than the carbonates, nitrates and hydroxides

• the metallic properties of the elements increases down the Group

The nitrates of Group 2 elements are decomposed by heat. Which of these nitrates in Group 2 has the highest thermal stability?

• Beryllium nitrate

• Magnesium nitrate

• Calcium nitrate

• Barium nitrate

Barium sulphate, BaSO₄ is less soluble than magnesium sulphate, MgSO₄. This is because

• BaSO₄ is covalent whereas MgSO₄ is ionic

• the lattice energy of BaSO₄ is higher than that of MgSO₄

• the hydration energy of Ba²⁺ is less than than of Mg²⁺

• the enthalpy of solution of BaSO₄ is more exothermic than that of MgSO₄