5.6.1 chemical energetics (thermochemistry) 🔥

Question 1

define (standard) enthalpy change of reaction

Answer 1

the energy change in a chemical reaction when the molar quantities of reactants specified in the chemical equation react to form products (at standard conditions)

Question 2

define standard enthalpy change of formation

Answer 2

the energy change when one mole of the substance is formed from its constituent elements at standard conditions

Question 3

define standard enthalpy change of combustion

Answer 3

the energy evolved when one mole of the substance is completely burnt in oxygen under standard conditions

Question 4

define standard enthalpy change of neutralisation

Answer 4

energy evolved when one mole of water is formed from the neutralisation between acid and base under standard conditions

Question 5

define standard enthalpy change of atomisation

Answer 5

energy absorbed when one mole of gaseous atoms is formed from the element under standard conditions

Question 6

define standard enthalpy change of hydration

Answer 6

energy evolved when one mole of the gasous ions in hydrated under standard conditions: Na+(g) -> Na+(aq)

Question 7

define standard enthalpy change of solution

Answer 7

energy change when one mole of the substance is completey dissolved in a solvent to form an infinitely dilute solution at standard conditions: NaCl(s) -> Na+(aq) + Cl-(aq)

Question 8

define bond energy

Answer 8

bond energy is the average energy absorbed to break one mole of covalent bonds in the gaseous state to form gaseous atoms under standard conditions

Question 9

define bond dissociation energy

Answer 9

bond dissociation energy is the energy required to break one mole of a particular covalent bond in a specific molecules in gasous state to form gaseous atoms

Question 10

define ionisation energy

Answer 10

ionisation energy is the energy absorbed when one mole of gaseous atoms loses one mole electrons to form one mole of singly positive gaseous cations

Question 11

define 1st/2nd electron affinity

Answer 11

1st/2nd electron affinity is the energy evolved/absorbed when one mole of gaseous atoms acquires one mole of electrons to form one mole of gaseous anions

Question 12

define lattice energy

Answer 12

lattice energy is the energy evolved when one mole of the solid ionic compound is formed from its constituent gaseous ions under standard conditions

Question 13

define entropy

Answer 13

entropy is a measure of disorder and number of ways energy can be distributed in a system