2 Know and be able to account for the trends in reactivity with water the relative solubility of the hydroxides and sulfates The Trend Hydroxides increase in solubility down the group Sulfates decrease in solubility down the group ID: 310666
Download Presentation The PPT/PDF document "Solubility of Group 2 Hydroxides and Sul..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Solubility of Group 2 Hydroxides and Sulfates
2.
Know and be able to account for the trends in reactivity with water
, the relative solubility of the hydroxides and sulfates
Slide2
The Trend
Hydroxides increase in solubility down the group.
Sulfates decrease in solubility down the group.Slide3
Factors Affecting Solubility
Solubility is dependent on
Lattice Dissociation Energy
Energy of HydrationSlide4
Lattice Dissociation Energy
This is the energy required to break the
organised
structure of the ionic lattice.
Energy is absorbed
ΔH is positive
Lattice Dissociation Energy governed by the distance between the
centres
of the ions.Slide5
Hydration of IonsSlide6
Energy of Hydration
Energy is released when an ion is hydrated.
ΔH is negative
Hydration enthalpy is governed by the size of the individual ions.
The force of attraction between small ions and water molecules is greater than large ionsSlide7
Problem 1
Calculated values for enthalpy of solution do not match measured values. The situation is complex!
Calculated Value
(kJ mol
-1
)
Data Book Value (kJ mol
-1
)
NaCl
+1
+3.9
KCl
+15
+17.2
RbCl
+10
+16.7
CsCl
+5
+17.9Slide8
Problem 2
The is no obvious relationship between enthalpy of solution and solubility.
Enthalpy of solution (kJ mol
-1
)
Solubility (
mol
/100g of water)
NaCl
+3.9
0.615
KCl
+17.2
0.418
RbCl
+16.7
0.781
CsCl
+17.9
1.13Slide9
Problem 3
The sign of the enthalpy change has no relationship to solubility.
Group 1 carbonates increase in solubility to a point, however barium carbonate is more soluble than strontium carbonate.
Values below are in kJ mol
-1
MgCO
3
CaCO
3
SrCO
3
BaCO
3
-25.3
-12.3
-3.4
+4.2Slide10
We need to consider entropy
Entropy is a measure of the amount of disorder in a system.
And that is all I understand for now!