Definitions

Question 1

Enthalpy change of reaction

Answer 1

Energy change in a chemical reaction when the molar quantities stated in chemical equation react under standard conditions

Question 2

Enthalpy change of formation of a substance

Answer 2

Energy change when 1 mole of pure substance in a specified state is formed from its constituent elements in their standard state under standard conditions

Question 3

Standard Enthalpy change of combustion of a substance

Answer 3

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

Question 4

Standard Enthalpy change of neutralisation between acid and a base

Answer 4

Energy change when an acid and base react to form one mole of water molecule under standard conditions

Question 5

Standard Enthalpy change of atomisation (element)

Answer 5

Energy absorbed when 1 mole of gaseous atoms is formed from its element under standard conditions

Question 6

Standard Enthalpy change of atomisation (compound)

Answer 6

Energy absorbed when one mole of the compound is converted to gaseous atoms under standard conditions

Question 7

Bond disassociation energy

Answer 7

Energy required to break one mole of that particular X-Y bond in a particular compound in gaseous state

Question 8

Bond energy

Answer 8

Average energy required to break one X-Y bond in the gaseous states

Question 9

First ionisation energy

Answer 9

Energy required to remove one mole of electrons from one mole of gaseous atoms to form one singly positively charged gaseous ion

Question 10

First electron affinity

Answer 10

Energy change when one mole of gaseous atoms acquires one mole of electron to form one mole of singly negatively charged ions

Question 11

Second electron affinity

Answer 11

Energy absorbed when one mole of singly negatively charged gaseous ion acquires one mole of electrons to form one mole of doubly negatively charged gaseous ions

Question 12

Lattice energy

Answer 12

Energy released when one mole of solid ionic compound is formed from its constituent gaseous ions under standard conditions

Question 13

Standard Enthalpy change of hybridisation

Answer 13

Energy released when one mole of gaseous ion is hydrated under standard conditions

Question 14

Standard Enthalpy change of solution

Answer 14

Energy change when one mole of substance is completely dissolved in a solvent to form an indefinitely dilute solution under standard conditions

Question 15

spontaneous process

Answer 15

process, that when once started, continue without any external assistance

Question 16

entropy (S)

Answer 16

measure of disorder (of matter and energy) in system. more disordered system is, the larger its entropy