5 Chem Energetics (I)

Question 1

Enthalpy change of atomisation

Answer 1

Enthalpy change when one mole of gaseous atoms is formed from the element

Question 2

Enthalpy change of formation

Answer 2

Enthalpy change when one mole of substance is formed from its constituent elements

Question 3

Enthalpy change of combustion

Answer 3

Enthalpy change when one mole of substance is completely burnt in oxygen

Question 4

IE

Answer 4

Enthalpy change when one mole of electrons is removed from one mole of gaseous atoms/ions

Question 5

EA

Answer 5

Enthalpy change when one mole of gaseous atoms/ions accepts one mole of electrons

Question 6

Lattice energy

Answer 6

Enthalpy change when one mole of solid ionic compound is formed from its constituent gaseous ions

Question 7

Bond energy

Answer 7

Average enthalpy change when 1 mole of covalent bonds is broken between atoms in a gaseous molecule

Question 8

Enthalpy change of neutralisation

Answer 8

Enthalpy change when 1 mole of water is formed from a neutralization reaction between an acid and an alkali

Question 9

Enthalpy change of hydration

Answer 9

Enthalpy change when one mole of gaseous ions is hydrated

Question 10

Enthalpy change of solution

Answer 10

Enthalpy change when one mole of the substance is completely dissolved in enough solvent such that no further enthalpy change occurs upon adding more solvent

ΔH(soln) = -LE + ∑ ΔH(hyd)

Question 11

Enthalpy change of reaction

Answer 11

Enthalpy change when molar quantities of reactants, as specified by the balanced chemical equation, react to form products

ΔH(r) = ∑ E(bonds broken) - ∑ E(bonds formed)

Question 12

Standard state

Answer 12

1. 273K/0°C
2. 1 bar/1.00*10^5 Pa
3. Most stable physical state
4. Concentration for (aq): 1 mol dm^-3

Question 13

Hess’ Law

Answer 13

Enthalpy change of a chemical reaction depends only on the initial and final states of the system and is independent of the reaction pathway taken