Part III

Question 1

ΔHr=?? When ΔHc are given.

Answer 1

ΔHc(rxt)-ΔHc(pdts)

Question 2

ΔHr=?? When ΔHf are given

Answer 2

ΔHf(pdts)-ΔHf(rxts)

Question 3

Steps to calculate ΔHsol

Answer 3

1. ΔHsol of solid to aq. ions
2. Write how the solid ionic compound is formed via LE
3. Connect rest of cycle using hydration

Question 4

What are the factors ΔHsol depends on?

Answer 4

1. Lattice energy
2. Hydration of ions

Therefore,
• ΔHhyd>LE
=> exo, soluble

•ΔHhyd endo, insoluble

Question 5

How to calculate B.E?

Answer 5

Total energy absorbed (broken)- total energy released (formed) =

a+(-b)

Question 6

5 steps for Born-Haber cycle

Answer 6

1. Write down Formation
2. Write down LE
3. ΔHatm
4. IE
5. EA

Question 7

What is the important thing to take note when predicting the stabilities of compounds?

Answer 7

•specify wrt what substance a compound is energetically stable or unstable

Question 8

Explain ‘kinetic and thermodynamic stability’ using diamond.

Answer 8

• Diamond is kinetically stable yet energetically unstable wrt to graphite
• large amt of energy req’ed to overcome the high Ae ensuring that diamond is kinetically stable