These two pages include all of the definitions of each standard enthalpy change, including key enthalpy terms, the born hater cycle, entropy, Gibbs’s free energy, spontaneous reactions, and exothermic and endothermic reactions. These pages include how to calculate such enthalpy’s.
Chapter 11 & 21, Measurements & Data Processing (IB Chemistry)
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STANDARD ENTHALPIES
#
Standard Enthalpy Exothermic/
Definition Symbol BOND ENTHALPY
change of: Endothermic
AVERAGE BOND ENERGY: the energy needed to break one mole of bonds in a
The enthalpy change when the reactants
Reaction Both gaseous molecule average over similar compounds
in the stoichiometric equation react to give
the products under standard conditions
AH = EH/bonds
broken-EHlbonds formed
The enthalpy change when one mole of a reactants) products)
compound is formed from its elements under Both
Formation
standard conditions
enthalpy change forbenhs brone
&H =
The enthalpy change when one mole of
Combustion a substance is burnt in excess oxygen Exothermic
under standard conditions
ACTIVATION ENERGY: the minimum amount of energy needed for reactant
molecules to have a successful collision and start the reaction
The enthalpy change when one mole
Neutralisation of water is formed by reacting an acid Exothermic
and alkali under standard conditions EXOTHERMIC
• the reactants are higher in energy than the products
• the reactants are therefore closer in energy to the transition sate
• lower activation energy (compared to endothermic)
• energy RELEASED
CALORIMETRY • BOND MAKING (energy released)
• is a technique used to measure changes in enthalpy of chemical reactions
• PRODUCTS more stable than REACTANTS
• made up of POLYSTYRENE DRINKING CUP, a VACUUM FLASK or
METAL CAN
ENDOTHERMIC
HEAT CAPACITY
·metee cur
•
•
•
•
the reactants are lower in energy than the products
reactants are further away in energy to the transition state
have higher activation energy compared to exothermic
energy ABSORBED
• BOND BREAKING (energy absorbed)
• PRODUCTS less stable than the REACTANTS
energe
(5)
&
Temperatoree
change
S
q = mxcxy
heat
↓& specific heat
transfereh(5) capacity /5gk')
mass
of solution
(g)
of H20
OZONE
OZONE H
(g) 0z(g)
= -
0
>
-
0 (g) +
,
FORMATION
.
0 (g) - 0 .
(g) +
02(g) H = + (vV)
OZONE
E 03(g)
,
BHt
(g) 29(g)
-
DEPLETION
=
+ 0 .
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