Chemical Energetics

Question 1

Mean bond enthalpy def

Answer 1

The average energy required to break one mole of bonds in gaseous molecules

Question 2

Enthalpy change def

Answer 2

(🔺H) the change in heat content at constant pressure

Question 3

Enthalpy def

Answer 3

A form of energy; the heat content that is stored within a chemical system (reacting molecules and the surroundings)

Question 4

Energy change of the solution eq

Answer 4

🔺Q = mc🔺T
m = mass of water or solution (1g = 1cm^3)
c = 4.2 (always given)
🔺T = temperature change

Question 5

Energy change for one mole of reaction eq

Answer 5

🔺Q/n

n = moles (mass/Mr)

Question 6

Molar enthalpy change eq

Answer 6

🔺H = -🔺Q/n
Unit = kJmol^-1

Question 7

Standard enthalpy change of reaction def

Answer 7

The enthalpy change when molar quantities react in standard conditions

Question 8

Standards enthalpy of atomisation

Answer 8

(Endothermic) the amount of energy required to produce one mole of gaseous atoms from an element in its state under standard conditions

Question 9

Lattice enthalpy

Answer 9

(Exothermic) the amount of energy released when one mole of ionic compound is formed from its constituent ions in the gas phase under standard conditions

Question 10

Electron affinity

Answer 10

the amount of energy released or absorbed when one electron is added to each atom or ion in one mole sample of gaseous atoms or ions under standard conditions

Question 11

Entropy

Answer 11

The quantitative measure of the degree of disorder (in terms of energy and space) in a system
E.g. High entropy = lots of disorder