Enthalpy of solution

Question 1

When do ionic solids dissolve well?

Answer 1

• in polar solvents

Question 2

What needs to happen in order for an ionic compound to dissolve?

Answer 2

• ionic lattice must be broken up
• requires an input of energy
  
  • =lattice enthalpy

Question 3

What is hydration?Describe the process

Answer 3

• hydration when the solvent solvating the ions is wgater
• cluster around the ions
• positive ions are surrounded by the negative ends of the dipolse of the water molecules and the negative ions are surrounded by the positive ends of the dipoles of the water molecules

Question 4

What is the trend of the enthalpy change of hydration?

Answer 4

• same trends as lattice enthalpy
  
  • the more negative for more highly charged ions and less negative for bigger ions

Question 5

What are the three processes in dissolving an ionic compound in water ?

Answer 5

• breaking the ionic lattice
  
  • gives separate gaseous ions
  • the lattice dissociation enthalpy has to be put in
• hydrating the cations (positive ions)
  
  • enthalpy of hydration is given out
• hydrating the anions
  
  • enthalpy of hydration is given out

Question 6

Describe the value of the enthalpy change of hydration?

Answer 6

• relatively small
• can be positive or negative