Solution & Hydration

Question 1

What is equation for ΔG?

Answer 1

ΔG = ΔH - TΔS

Question 2

What happens when ionic lattice dissolves?

Answer 2

Breakdown of ionic lattice into gaseous ions
Hydration of the ions

Question 3

What affects lattice enthalpy & hydration enthalpy?

Answer 3

Ionic size - smaller ions more attractive
Ionic charge

Question 4

What is equation for ΔHsol?

Answer 4

ΔHsol = -ΔHLE + ΔHhyd

Question 5

Calculate ΔG for for following at 25℃
CaO(s) + H2O(l) —> Ca(OH)2(s)
CaO ΔH=-635.5 ΔS=39.7
H2O ΔH=-285.9 ΔS=70.1
Ca(OH)2 ΔH = -986.9 ΔS=76.1

Answer 5

ΔHreaction= ΔHproducts - ΔHreactants
ΔHreaction= -986.9 - (-635.5-285.9)=-65.5kJmol-1
ΔS = ∑ΔSproducts - ∑ΔSreactants
ΔS= 76.1-(30.7+70.1)= -33.7J = -0.0337kJ
ΔG = ΔH-TΔS
ΔG = -65.5-(298x-0.0337)= -55.5

Question 6

What is feasibility of reaction when:
ΔH = +
ΔS = -

Answer 6

Never

Question 7

What is feasibility of reaction when:
ΔH = -
ΔS = +

Answer 7

Always

Question 8

What is feasibility of reaction when:
ΔH = -
ΔS = -

Answer 8

Only at low temperature

Question 9

What is feasibility of reaction when:
ΔH = +
ΔS = +

Answer 9

Only at high temperature