Thermodynamics A2 Flashcards Preview

Chemistry A-Level > Thermodynamics A2 > Flashcards

Flashcards in Thermodynamics A2 Deck (16):
1

Define the enthalpy of formation

The standard enthalpy change which occurs when one mole of a compound is produced from its constituent elements in standard conditions of 298k and 100kPa

2

Define ionisation energy

The standard enthalpy change which occurs when one mole of gaseous atoms become one mole of gaseous ions, producing one mole of electrons

3

Define enthalpy of atomisation

The standard enthalpy change for the formation of one mole of gaseous atoms from the element in its standard state under standard conditions

4

Define mean bond enthalpy

The standard enthalpy change which occurs when one mole of gaseous molecules each breaks a covalent bond to from two free radicals, averaged over different compounds

5

Define electron affinity

The standard enthalpy change which occurs when a mole of electrons is added to one mole of gaseous atoms to form one mole of gaseous ions

6

Describe the steps for the formation of an ionic compound from its elements

Atomisation of first element, atomisation of second element, ionisation energy of first, electron affinity of the second, formation of lattice energy

7

Describe the steps for the enthalpy of hydration for an ionic compound

Lattice dissociation enthalpy, hydration enthalpy of first element, hydration enthalpy of second element

8

Describe the process of hydration

Water molecules cluster around the ions due to its polar sides

9

Define enthalpy of hydration

The standard enthalpy change which occurs when water molecules surround one mole of gaseous ions

10

When is a reaction more likely to occur spontaneously

if the final product is more randomly distorted than the reactants

11

Why are gases more likely to react spontaneously

They are more random than liquids or solids

12

What is the entropy of a system

The randomness of a system, with the symbol S, given in standard conditions of 298k and 100kPa

13

What does a positive value for entropy mean

The reaction will occur spontaneously

14

How to calculate entropy changes of a reaction

Sum of entropy values of products - Sum of entropy values of reactants

15

What is the Gibbs free energy

∆G = ∆H - T∆S. If ∆G is negative, the reaction is feasible

16

What occurs if ∆G is zero

The reaction is feasible