Enthalpy changes Flashcards
1
Q
Activation energy
A
minimum energy required for a reaction to occur
2
Q
Bond enthalpy
A
- enthalpy change that takes place
- when 1 mole of a specified bond is broken into its atoms
- in the gas phase
3
Q
Endothermic
A
- reaction
- enthalpy of products > enthalpy of the reactants
- (ΔH is positive)
4
Q
Enthalpy (H)
A
heat content of a chemical measured at constant pressure
5
Q
Exothermic
A
- reaction
- enthalpy of the products < enthalpy of the
reactants - (ΔH is negative)
6
Q
Hess’ Law
A
- enthalpy change of a reaction is independent of the route
- only depends on initial and final stages
7
Q
Mean bond enthalpy
A
- enthalpy change
- 1 mole of a specified bond is broken into its atoms in the gas phase
- averaged over many compounds containing that bond
8
Q
Specific heat capacity (c)
A
- energy in Joules required to raise the temperature
- of 1g of a substance by 1 K
9
Q
Standard conditions
A
- Pressure = 100kPa
- temperature = 298K (25oC)
- aqueous solutions of concentration 1.00 mol dm-3
10
Q
The standard enthalpy change of COMBUSTION ΔcH
A
- enthalpy change
- 1 mole of a substance reacts completely with oxygen
- measured under standard conditions
11
Q
The standard enthalpy change of FORMATION ΔfH
A
- enthalpy change
- 1 mole of a substance is formed from its elements
- measured under standard conditions
12
Q
The standard enthalpy change of REACTION ΔrHӨ
A
- enthalpy change
- chemical reaction for the quantities in the chemical equation
- measured under standard conditions
13
Q
The standard enthalpy change of NEUTRALISATION ΔneutH
A
- enthalpy change
- chemical reaction between aqueous acid and an aqueous alkali
- to produce 1 mole of water
- measured under standard conditions
