Thermochemistry

Question 1

Hess’ law

Answer 1

enthalpy change of a chemical reaction is the same, regardless of the reaction take place in single step or series of steps

Question 2

Lattice energy

Answer 2

Amount of energy released when 1 mole of solid crystal lattice is formed from its oppositely charged gaseous ion under standard condition

Question 3

Standard enthalpy change of combustion

Answer 3

Amount of energy released when 1 mole of substance is burned in excess of air under standard condition

Question 4

Standard enthalpy change of formation

Answer 4

Amount of energy released when 1 mole of substance is burned in excess of air under standard condition

Question 5

Standard enthalpy change of neutralisation

Answer 5

Amount of energy released when 1 mole of hydrogen ion from acid reacts with 1 mole of hydroxide ion from alkali to form water under standard condition

Question 6

Standard enthalpy change of atomisation

Answer 6

Amount of energy absorbed when 1 mole of gaseous atom is formed from its element under standard condition

Question 7

First ionisation energy

Answer 7

Amount of energy absorbed when 1 mole of electron is removed from a gaseous atom to form unipositively charged ion under standard condition

Question 8

First electron affinity

Answer 8

Amount of energy released when 1 mole of electron is received from a gaseous atom to form uninegatively charged ion under standard condition

Question 9

Enthalpy change of hydration

Answer 9

Amount of energy liberated when 1 mole of gaseous ion dissolved in water to form aqueous ionic solution under standard condition

Question 10

Enthalpy change of solution

Answer 10

Amount of energy changes occured when 1 mole of solute is dissolved in excess water to form infinite dilute solution under standard condition

Question 11

Bond energy

Answer 11

Heat absorbed to break a covalent bond between a covalent compound

Question 12

The more exothermic the enthalpy change of formation

Answer 12

The more stable the compound formed

Question 13

Strength of lattice energy depend on

Answer 13

directly proportional to charge of the ions and inversely proportional to inter-ionic radii

Question 14

Magnitude of enthalpy of hydration depend on

Answer 14

directly proportional to charge of ion and inversely proportional to ionic radius

Question 15

If enthalpy change of solution is endothermic

Answer 15

solutes are sparingly soluble in water

Question 16

If enthalpy change of solution is exothermic

Answer 16

solutes are mostly soluble in water