Presentation on theme: "GROUP II. Thermal stability of Group II carbonates and nitrates. MgCO 3, Mg(NO 3 ) 2 CaCO 3, Ca(NO 3 ) 2 SrCO 3, Sr(NO 3 ) 2 BaCO 3, Ba(NO 3 ) 2 - Thermal."— Presentation transcript:
Thermal stability of Group II carbonates and nitrates. MgCO 3, Mg(NO 3 ) 2 CaCO 3, Ca(NO 3 ) 2 SrCO 3, Sr(NO 3 ) 2 BaCO 3, Ba(NO 3 ) 2 - Thermal stability increase, more difficult to decompose. - Ionic radius increase, - charge density decrease, - more difficult to distort the large CO 3 2- and NO 3 - anion. - Compound more difficult to decompose.
In decomposition, the large CO 3 2- and NO 3 - anions are first distorted decompose into smaller O 2- anion. This distortion produced by metal cation (M 2+ ) which forms a stronger bond with the small O 2- ion produce the more stable Group II oxide.
Solubility of Group II sulphates and oxides When an ionic compound dissolved in water : MX(s) + aq M + (aq) + X - (aq) H sol < 0 This process involves 2 imaginary stages: 1) MX(s) M + (g) + X - (g),- H latt > 0 2) M + (g) + X - (g) + aq M + (aq) + X - (aq), H hyd < 0 Going down the group, ionic radius increase, lattice energy decrease (less exothermic) Hence step 1 becomes less endothermic and step 2 becomes less exothermic. Change of H hyd is more compare to lattice energy. Going down the group, H hyd decrease more compare to lattice energy. Solubility in water decrease. CompoundSolubility in water MgSO 4 Very soluble CaSO 4 Sparingly soluble SrSO 4 Insoluble BaSO 4 Insoluble