Thermodynamics

Question 1

Definition for enthalpy of atomisation?

Answer 1

Enthalpy change when one mole of gaseous atoms is formed from an element in its standard state

Question 2

Equation for atomisation of Na, Br2?

Answer 2

Na(s) ——-> Na(g)
Br2(l) ——-> 2Br(g)

Question 3

△H for bond enthalpy equals…

Answer 3

2 x △Hat

Question 4

Definition for first electron affinity?

Answer 4

Enthalpy change when one mole of gaseous atoms is converted into a moles of gaseous ions, each with a single -ve charge under standard conditions

Question 5

Definition for second electron affinity?

Answer 5

Enthalpy change when one moles of electrons is added to a mole of gaseous ions each with a single -ve charge to form a mole of ions each with a -2 charge

Question 6

Definitions for first ionisation enthalpy?

Answer 6

Enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to give one mole of gaseous ions each with a single +ve charge

Question 7

Equation for first + second electron affinity for oxygen?
Exothermic or endothermic?

Answer 7

O(g) + e- ——> O-(g) EXO.
O-(g) + e- ——> O2-(g). ENDO.

Question 8

Definition for lattice formation enthalpy?

Answer 8

Enthalpy change when one mole of a solid ionic compound is formed from its gaseous ions

Question 9

Definitions for lattice dissociation enthalpy?

Answer 9

Enthalpy change when one mole of a solid ionic compound dissociates into its gaseous ions

Question 10

Equation for lattice formation enthalpy for NaCl?

Answer 10

Na+(g) + Cl-(g) ——> NaCl(s)

Question 11

Explain why NaCl has a more exothermic lattice enthalpy of formation than NaI?

Answer 11

• Cl- has a smaller ionic radius than I-
• Stronger attraction between Cl- and Na+
• More exothermic in NaCl

Question 12

Predict which ionic compound between NaCl and AlCl3 will have the most endothermic lattice enthalpy of dissociation?

Answer 12

• Al3+ has a larger charge than Na+ so a smaller radius
• Al3+ has a stronger attraction between the Cl-
• AlCl3 has a higher endothermic dissociation

Question 13

When does covalent character occur in an ionic compound?

Answer 13

• When positive ion is small with high charge (polarising)
• When negative ion is large with high charge (polarisable)

Question 14

Definition for enthalpy of solution?

Answer 14

Enthalpy change when one mole of solute dissolves to form its aqueous ions

Question 15

Equation for enthalpy of solution for CaCl2?

Answer 15

CaCl2(s) ——> Ca2+(aq) + 2Cl-(aq)

Question 16

Definition for enthalpy of hydration?

Answer 16

Enthalpy change when one mole of gaseous ions is converted into one mole of aqueous ions

Question 17

Equations of enthalpy of hydration for Cl-?

Answer 17

Cl-(g) ——> Cl-(aq)

Question 18

USE FRIDAY QUIZ SHEET FOR QUESTIONS

Question 19

Construct Hess cycle using enthaply of solution equation for CaCl2

Answer 19