1.1 - Thermodynamics (INORGANIC)

Question 1

Enthalpy of formation.

Answer 1

Enthalpy change when one mole of a compound is made from its elements In standard conditions , elements and products being standard state

Question 2

Enthalpy of combustion.

Answer 2

Enthalpy change one mole of a compound is burned is excess oxygen under standard conditions with all reac and products being in their standard state.

Question 3

Enthalpy of atomisation

Answer 3

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

Question 4

Mean bond enthalpy

Answer 4

The enthalpy change when one mole of gaseous molecules each break a covalent bond to form 2 free radicals averaged over a diff range of compounds

Question 5

2MBE= 1EAT

Question 6

First ionisation enthalpy

Answer 6

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

Question 7

Second ionisation enthalpy

Answer 7

Enth change one mole of electron is removed from 1+ gas. Ions to give one mole of gas ions each each 2+ charge

Question 8

First / second electron affinity

Answer 8

Enthalpy change when one mole of gaseous atoms is converted into a mole of gaseous ions each with a single negative charge
////
One mole of e- is added to a mole of gaseous ions each with a single -ve charge to form a mole of ions with 2- charge

Question 9

Lattice formation / dissociation enthalpy

Answer 9

Enthalpy change when one mole of solid ionic compound is formed from its gaseous ions.
////
One mole of solid ionic compound dissociates into its gaseous ions

Question 10

Enthalpy of hydration

Answer 10

Ent change when one mole of gaseous ions is converted into one mole of aq ions

Question 11

Enthalpy of solution

Answer 11

Ent change when one mole of solute dissolves in enough solvent to form a solution in which the ions are far enough apart not to interact with each other

Question 12

Why MgO is more exothermic than MgCl2 example.

Answer 12

O2- has a greater negative charge
O2- has a Greater attraction to Mg2+ ions

Question 13

CRAM

Answer 13

Charge on ions
Size of ions
Attraction
More or less exothermic

Question 14

Thereotical vs experimental model

Answer 14

Perfect ionic model vs born haber cycle
Perfect spheres ions point charged vs ions are polarisable
Purely ionic compound
Covalent character

Question 15

Why AgI experimental value is greater than theoretical.

Answer 15

-AgI has covalent character
-stronger bonding

Question 16

Enthalpy of solution

Answer 16

The enthalpy change when one mole of solute dissolves in enough solvent to form a solution of aq ions where they are far apart enough not to interact with each other.

Question 17

Why do chemical reactions take place?

Answer 17

To be feasible and spontaneous

Question 18

Factors determining feasibility

Answer 18

1)temp
2)enthalpy(exo)
3)entropy

Question 19

Entropy units and definition
1)entropy for MgCl2(s)&raquo_space; Mg(g) + Cl(g)

Answer 19

1) J K-1 mol-1
2)amout of disorder in a system.
3)more disorder

Question 20

Suggest how the evaporation of water is endothermic and spontaneous.

Answer 20

More disorder
Increase in entropy
🔺G < 0

Question 21

Explain why theorethical enthalpy is different from born haber cycle.(2)

Answer 21

Ions are point charges
Has covalent character

Question 22

Effect on Kp for increasing temp on endo reaction.

Answer 22

Increase , high temp favour endothermic reaction. More products made

Question 23

High pressure issue?

Answer 23

High pressure is expensive (1) and slow(2)

Question 24

Effect of reactant yield with equal moles if increased volume

Answer 24

Increase

Question 25

Why is Mg2+ enthalpy of hydration greater than Na+.(2)

Answer 25

-greater charge and smaller ion
-greater attraction of h20

Question 26

Why combustion and formation enthalpy of water is SAME .(1)
Why it may be diff (1)

Answer 26

1.same number of bonds broke and formed and same reaction
2. MBE and actual bond enthalpy is diff

Question 27

Effect of decreasing temp to make a reaction more feasible.

Answer 27

• delta G is negative
  —deltaST will be negative