Born Haber EP 12th May

Question 1

Explain what is meant by the term average bond enthalpy

Answer 1

average enthalpy change that takes place when 1 mole of bonds is broken in gaseous molecules

Question 2

Calculate bond enthalpy of F-F bond

Answer 2

reactants - products

Question 3

Explain what is meant by the term enthalpy change of hydration

Answer 3

Enthalpy change when 1 mole of gaseous ions dissolve in excess water

Question 4

Predict how enthalpy changes of hydration of F- and Cl- would differ

Answer 4

F- is a smaller ion that Cl- therefore enthalpy of hydration of F- will be more EXOTHERMIC as GREATER ATTRACTION TO H2O

Question 5

Predict, with a reason, whether forward reaction is exothermic or endothermic

Answer 5

forward reaction will be exothermic, as Kp decreases as temperature increases

Question 6

The chemist increases the pressure, state and explain in terms of Kp how you’d expect the equilibrium position to change

Answer 6

The equilibrium position will shift to the right,
So the denominator of Kp will increase more than numerator,
so numerator increases to restore Kp

Question 7

The first ionisation energy of sodium is more endothermic than potassium, explain why

Answer 7

sodium has a SMALLER ATOMIC RADIUS , so outer electron experiences more attraction

Question 8

The lattice enthalpy of sodium oxide is more exothermic than that of potassium oxide

Answer 8

Ionic radius of Na+ is smaller, so sodium oxide has STRONGER ionic bonds than potassium oxide

Question 9

The chemist repeats the experiment at a different temperature.
Kp value is greater, explain whether the temperature in the second experiment is higher or lower than 1000K

Answer 9

greater Kp value means equilibrium position shifts to the right, the temperature is lower as forward reaction exothermic

Question 10

Explain the significance of the expression Kp»1

Answer 10

equilibrium position to the RIGHT