Energetics

Question 1

Enthalpy of atomisation of element

Answer 1

Energy required to form 1 mole of gaseous atoms from the element in its standard state under standard conditions

Question 2

Atomisation enthalpy of compounds

Answer 2

Energy required to form gaseous atoms from 1 mole of the compound in its standard state under standard condition

Question 3

bond energy

Answer 3

average energy required to break 1 mole of covalent bond between 2 atoms in gaseous state

Question 4

why using bond energy is inaccurate

Answer 4

bond energy is average value (if applicable: does not include enthalpy change for change of physical state)

Question 5

Enthalpy change of combustion

Answer 5

Energy released when 1 mole of substance is completely burnt in excess oxygen under standard conditions

Question 6

Enthalpy change of formation

Answer 6

Enthalpy change when 1 mole of substance is formed from its constituent elements in their standard states under standard conditions

Question 7

Enthalpy change of hydration

Answer 7

Energy released when 1 mole of free gaseous ions is hydrated under standard condition

Question 8

Lattice Energy

Answer 8

Energy released when 1 mole of solid ionic compound is formed from its constituent gaseous ions

Question 9

enthalpy change of neutralistation

Answer 9

Energy released when 1 mole of water is formed in a neutralisation reaction between an acid and a base under standard conditions

Question 10

enthalpy change of neutralisations with weak acid/base

Answer 10

less exothermic since energy is absorbed to dissociate/ionise the undissociated/unionised weak acid/ base

Question 11

Enthalpy change of solution

Answer 11

energy change when 1 mole of substance completely dissolve in an infinite volume of solvent under standard condition

Question 12

entropy, S

Answer 12

measure of level of disorderliness or randomless

Question 13

factors affecting entropy

Answer 13

1. change in phase (solid to liquid to gas)
   level of disorderliness increases as there are more ways which the energy can be distributed among the particles
2. mixing of gas particles
   increase in volume to maintain constant pressure, entropy will increase because there are more ways in which the energy can be distributed among the particles
3. increase in number of gas particles
   more ways in which the energy can be distributed among the particles
4. change in temperature
   temp increase, energy content increase, more ways in which the energy can be distributed among the particles

Question 14

Spontaneous process

Answer 14

process that takes place naturally in the direction stated without a need for continuous external input of energy

Question 15

both enthalpy and entropy are positive

Answer 15

reaction becomes spontaneous at high temperatures

Question 16

both enthalpy and entropy are negative

Answer 16

exothermic reactions that are spontaneous at low temperatures

Question 17

enthalpy negative, entropy positive

Answer 17

spontaneous at all temp

Question 18

enthalpy positive, entropy negative

Answer 18

non spontaneous at all temp