Energetics

Question 1

Bond enthalpy of water

Answer 1

H2O (g) -> OH (g) + H (g)

Question 2

Mean bond enthalpy of water

Answer 2

1/2H2O (g) -> 1/2O (g) + H(g)

Question 3

Measuring enthalpy

Answer 3

Use a pipette

Question 4

When discussing lattice energy

Answer 4

Discuss in terms of negativity

Question 5

Small charge

Answer 5

Not very polarising

Not very polarisable

Question 6

Why is there no 3rd ionisationenervh

Answer 6

• very endothermic

* not compensated for by electron affinities and lattice energy

Question 7

When you mention exothermique

Answer 7

State that temperature increases

Question 8

When discussing order

Answer 8

Discuss in number of moles

Question 9

ΔSsurr outweighs

Answer 9

ΔSsys

Question 10

Molar entropy varies with

Answer 10

Temperature

Question 11

when predicting changes of entropy

Answer 11

observe number of moles each side of the eqn (greater moles = greater entropy)

Question 12

why might an ionic substance be insoluble in water

Answer 12

enthalpy of solution is too endothermic

Question 13

units of Gibbs free energy

Answer 13

kJ/mol

Question 14

thermodynamic stability

Answer 14

unstable if change in Gibbs Free energy is less than 0

Question 15

why don’t endothermic reactions disobey they second law of thermodynamics?

Answer 15

• disorder of system increases
• disorder of surroundings decreases
• increase in system outweighs decrease in surroundings
• total entropy increases