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What is the order of solubility of carbonates ,sulphates & hydrogencarbonates in metal carbonates , metal sulphates and metal hydrogencarbonates...??? I have my aieee exams approaching !!! Help me yaar... Three cheers ***

What is the order of solubility of carbonates ,sulphates & hydrogencarbonates in metal carbonates , metal sulphates and metal hydrogencarbonates...???


 


I have my aieee exams approaching !!! Help me yaar... Three cheers ***

Grade:12

1 Answers

ruchi yadav
askIITians Faculty 27 Points
10 years ago
  • Explanation of solubility trends(usually dealt with later in course e.g. in UK A2 advanced level)

    • The simplest approach is to consider thetwo enthalpy change trends.

      • Theprocess of dissolving can be analysed in terms of two theoretical stagese.g. for simple cation–anion ionic compound.

        • In the arguments outlined belowMn+could be Gp1 or Gp2 metal cation etc.,Xn–could be halide, oxide, hydroxide, sulphate, carbonate anion etc., and n is the charge on ion – the n's may be different or the same):

      • (1)Mn+aXn–b(s)==> aMn+(g)+ bXn–(g)(breaking the lattice apart into its constituent ions)

      • This process is always endothermic, and is called thelattice enthalpy. Its usually defined in the opposite direction by saying it is 'the energy released when 1 mole of an ionic lattice is formed from its constituent gaseous ions' (at 298K, 1 atmos./101kPa pressure).

      • *The lattice enthalpy decreases down the group as the cation radius increases (anion radius constant for a particular seriese.g. sulphates). Therefore, energetically, the solvationin terms of lattice energy is increasingly favoured down the group.

      • (2) Mn+(g)+ aq==>Mn+(aq)andXn–(g)+ aq==>Xn–(aq)

        • Representing the solvation–hydration of ions.

      • The equations above represent to the two 'hydration enthalpies', the heat released when an isolated gaseous ion becomes solvated by water to form an aqueous solution (1M, 298K, 1 atmos./101kPa pressure)

      • *The hydration enthalpy for the cation decreases down the group as the radius gets larger. Therefore, energetically, the solvation is less favoured down the group as the cation radius increases.

    • * In both cases the numerical enthalpy value increases the smaller the radii as charges closer,and the greater the ionic charge (constant for a series), both factors increase the electrical attraction of either cation–anion in the crystal or ion–water in aqueous solution.


Thank You
Ruchi
Askiitians Faculty

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