2 Thermal stability of Group II carbonates and nitrates. MgCO3 , Mg(NO3)2CaCO3 , Ca(NO3)2SrCO3 , Sr(NO3)2BaCO3 , Ba(NO3)2- Thermal stability increase, more difficult to decompose.- Ionic radius increase,- charge density decrease,more difficult to distort the large CO32- and NO3- anion.Compound more difficult to decompose.
3 In decomposition, the large CO32- and NO3- anions are first distorted decompose into smaller O2- anion.This distortion produced by metal cation (M2+) which forms a stronger bond with the small O2- ion produce the more stable Group II oxide.
4 Solubility of Group II sulphates and oxides CompoundSolubility in waterMgSO4Very solubleCaSO4Sparingly solubleSrSO4InsolubleBaSO4When an ionic compound dissolved in water :MX(s) + aq M+(aq) + X-(aq) Hsol < 0This process involves 2 imaginary stages:1) MX(s) M+(g) + X-(g), -Hlatt > 02) M+(g) + X-(g) + aq M+(aq) + X-(aq), Hhyd < 0Going 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 Hhyd is more compare to lattice energy.Going down the group, Hhyd decrease more compare to lattice energy.Solubility in water decrease.
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