Anita Akweshie-
the group 2 nitrates and carbonates become more thermally stable
going down the group
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what attributes the increased stability of group 2 nitrates and carbonates going down the group
charge density of the cation
polarisation of the anion
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what kind of ions are formed by group 2 metals
2+
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the size of metal cations increase
down the group
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the greatest charge density is found where and why
the top of the group due the small ionic radii
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what is the relationship between ionic size and charge density
inversely proportional
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the greater the charge density of an ion, the
greater the polarising effect
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what is the relationship between the charge density and the polarising effect of an ion
directly proportional
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what is polarisation of an ion
the distortion of an ion due to its electrons being attracted away from its nucleus
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what is the relationship between the polarisation of an anion and the amount of heat required to thermally decompose it
inversely proportional
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what is the effect of polarisation
decreases the thermal stability
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explain why thermal stability of nitrates and carbonates increases down the group
down the group, the cation becomes larger
thus has a smaller charge density
and a smaller polarising effect on the anion
the anion is less polarised
therefore more heat is required to thermally decompose them
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the solubility of group 2 hydroxides increase
down the group
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the solubility of group2 sulfates increase
up the group
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compounds that have very low solubility are said to be
sparingly soluble
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the definition of standard enthalpy or solution
the energy absorbed or released when 1 mole of ionic solid dissolves in enough water to form a dilute solution under standard conditions
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true / false
the standard enthalpy of solution can be either exothermic or endothermic
true
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what is the standard enthalpy of hydration expressed as an equation
the sum of the lattice energy and the standard enthalpy change of hydration
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the definition of lattice (formation) energy
the energy released when gaseous ions combine to form one mole of an ionic compound under standard conditions
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lattice energy is always
exothermic
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definition of the standard enthalpy of hydration
the energy released when gaseous ions dissolve in enough water to form a dilute solution under standard conditions
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the standard enthalpy of hydration is always
exothermic
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going down the group, the lattice energy of the ionic compounds
decreases
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explain the trend of lattice energy decreasing down the group
going down, the positively charged cations become larger
there is more space between the negatively and positively charged ions in the ionic compound so there are weaker attractive forces between the ions
there are weaker electrostatic forces between the ions
less energy released upon formation of the ionic compound from its gaseous ions
therefore lattice energy becomes less exothermic
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going down the group, the standard enthalpy of hydration
decreases
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explain the trend in decrease of standard enthalpy of hydration down the group
cationic radius increases down the group
the ion-dipole bonds between the cations and water molecules get weaker
meaning less energy is released when the gaseous group 2 ions become hydrated
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for group 2 hydroxides the enthalpy change of solution is
exothermic going down the group
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explain why for the G2 hydroxides the enthalpy change of solution is exothermic going down
hydroxide ions are relatively small ions
the lattice energy falls faster than the enthalpy of hydration
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for group 2 sulfates the enthalpy change of solution is more
endothermic going down the group
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explain why for the G2 sulfates the enthalpy change of solution is more endothermic going down the group
sulfate ions are relatively large ions
the lattice energy falls slower than the enthalpy change of hydration
the enthalpy change of solution will become more endothermic going down the group
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the more exothermic the enthalpy change of solution, the
more soluble the compound
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what is the reason why sulfates become less soluble and hydroxides more soluble going down the group
the more exothermic the enthalpy change of solution, the more soluble the compound
