Enthalpy of Solution Cycles - Thermodynamics Pt B (3.4)

Question 1

When ionic substances dissolve, they dissociate into ions, what does this depend on?

Answer 1

Lattice Enthalpy

Question 2

What is the standard enthalpy of solution?

Answer 2

• enthalpy change when 1 mole of a solute dissolves in water to form an infinitely dilute solution (USC)

Question 3

The more exothermic the enthalpy of solution, the more soluble the sunstance. True or False?

Answer 3

True

Question 4

What is enthalpy of solution?

Answer 4

• when 1 mole of solute dissolves in water to form an infinitely dilute solution (USC)

Question 5

Bond Formation is exothermic therefore enthalpy of hydration is…

Answer 5

Negative

Question 6

What is formed with enthalpy of hydration?

Answer 6

• ion-dipole intermolecular forces

Question 7

What are the trends in group 1 and 2 compounds?

Answer 7

• depend on mainly reactivity & redox reactions
• solubility of group 1 vs group 2 compounds
• solubility of group 2 hydroxides
• solubility of group 2 sulfates
• thermal stabilty of group 2 carbonates
• thermal stability of group 2 nitrates

Question 8

Group 1 salts are usually more soluble than group 2 salts. True or False?

Answer 8

True - NaCl vs MgCl2

• G1 salts have weaker ionic bond and requires less energy to break the bond

Question 9

Group 2 metal hydroxides increase in solubilty down the group. True or False? Explain your answer

Answer 9

True - Mg(OH)2 vs Ba(OH)2

• As the ions get bigger it becomes easier to break the ionic bond
• The difference in lattice enthalpy is greater than the difference in hydration enthalpy so ΔHsol is more exothermic down the group

Question 10

What happens in a polarised ionic bond?

Answer 10

• electron density pulled towards the cation
• stronger ionic bond
• small, highly charged cation
• large, polarisable anion

Question 11

Solubility of group 2 metal sulfates decreases down the group. True or False? Explain your answer

Answer 11

True

• sulfate is very polarisable
• Energy required to break the bond decreases down the group as the ions get bigger
• The lattice enthalpy decreases more slowly this time due to polarisation (this would cause enthalpy of solution value to decrease)

Question 12

Group 2 metal carbonates become more stable down the group. True or False?

Answer 12

True - carbonate ion = more polarisable, so enthalpy chnage decreases more slowly

Question 13

Group 1 metal carbonates are generally more stable than group 2 metal carbonates. True or False?

Answer 13

True - group 2 metals are more polarising so the energy required to break the M - CO3 bond is greater