II.3 Predicting Whether a Rx is Spontaneous or Not p. 43 - 49.
30
II.3 Predicting Whether a Rx is Spontaneous or Not p. 43 - 49
-
Upload
cole-moser -
Category
Documents
-
view
214 -
download
1
Transcript of II.3 Predicting Whether a Rx is Spontaneous or Not p. 43 - 49.
II.3 Predicting Whether a Rx is
Spontaneous or Not p. 43 - 49
Spontaneous
a change that occurs by itself, without any help
some rxs are spontaneous, others are not
Enthalpy
∆H (heat)
systems drive towards the lowest possible energy state
endothermic rx = +∆H
exothermic rx = -∆H
Entropy
∆S
possibility for disorder, the drive towards randomness
increasing entropy = +∆S
decreasing entropy = -∆S
There are 2 drives in any rx:
the tendency for a rx to go to the side with MAXIMUM RANDOMNESS (MAX. ENTROPY)
the tendency for a rx to go to the side with MINIMUM ENERGY (MIN. ENTHALPY)
Ex. showing an Increase ∆S:
gas formed from a solid
gas formed from a solution
# mol of gaseous product is greater than # mol of gaseous reactant
when a solid dissolves in water
Ex. of Minimum Enthalpy:
PE
Time
Exofavoursproducts
Ex. of Minimum Enthalpy:
PE
Time
Exofavoursproducts
PE
Time
Endofavours
reactants
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic favours _______
(+)favours _______
(-) exothermic favours _______
(-)favours _______
(+) endothermic
favours _______
(+)favours _______
(+) endothermic
favours _______
(-)favours _______
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic Favours products
(+)favours products
(-) exothermic favours _______
(-)favours _______
(+) endothermic
favours _______
(+)favours _______
(+) endothermic
favours _______
(-)favours _______
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic Favours products
(+)favours products
Spontaneous Rx goes 100%
(-) exothermic favours _______
(-)favours _______
(+) endothermic
favours _______
(+)favours _______
(+) endothermic
favours _______
(-)favours _______
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic Favours products
(+)favours products
Spontaneous Rx goes 100%
(-) exothermic favours products
(-)favours reactacts
(+) endothermic
favours _______
(+)favours _______
(+) endothermic
favours _______
(-)favours _______
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic Favours products
(+)favours products
Spontaneous Rx goes 100%
(-) exothermic favours products
(-)favours reactacts
SpontaneousRx goes to Equil.
(+) endothermic
favours _______
(+)favours _______
(+) endothermic
favours _______
(-)favours _______
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic Favours products
(+)favours products
Spontaneous Rx goes 100%
(-) exothermic favours products
(-)favours reactacts
SpontaneousRx goes to Equil.
(+) endothermic
favours reactants
(+)favours products
(+) endothermic
favours _______
(-)favours _______
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic Favours products
(+)favours products
Spontaneous Rx goes 100%
(-) exothermic favours products
(-)favours reactacts
SpontaneousRx goes to Equil.
(+) endothermic
favours reactants
(+)favours products
SpontaneousRx goes to Equil.
(+) endothermic
favours _______
(-)favours _______
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic Favours products
(+)favours products
Spontaneous Rx goes 100%
(-) exothermic favours products
(-)favours reactacts
SpontaneousRx goes to Equil.
(+) endothermic
favours reactants
(+)favours products
SpontaneousRx goes to Equil.
(+) endothermic
favours reactants
(-)favours reactants
The Probability of a Rx Occuring:∆H ∆S Spontaneity(-)
exothermic Favours products
(+)favours products
Spontaneous Rx goes 100%
(-) exothermic favours products
(-)favours reactacts
SpontaneousRx goes to Equil.
(+) endothermic
favours reactants
(+)favours products
SpontaneousRx goes to Equil.
(+) endothermic
favours reactants
(-)favours reactants
Rx will NOT occur
Ex: 2NH3(g)+ 92 kJ➔N2(g) +
3H2(g)
∆H favours___________
∆S favours___________
therefore the rx ________________
Ex: 2NH3(g)+ 92 kJ➔N2(g) +
3H2(g)
∆H favours reactants
∆S favours products
therefore the rx ________________
Ex: 2NH3(g)+ 92 kJ➔N2(g) +
3H2(g)
∆H favours reactants
∆S favours products
therefore the rx goes to equilibrium
BaCO3(s) ➔BaO(s) + CO2(g) ∆H=600kJ
∆H favours___________
∆S favours___________
therefore the rx ________________
BaCO3(s) ➔BaO(s) + CO2(g) ∆H=600kJ
∆H favours reactants
∆S favours products
therefore the rx ________________
BaCO3(s) ➔BaO(s) + CO2(g) ∆H=600kJ
∆H favours reactants
∆S favours products
therefore the rx goes to equilibrium
3H2(g)+ CO(g)➔CN4(g) + H2O(g)
∆H = -51 kJ
∆H favours___________
∆S favours___________
therefore the rx ________________
3H2(g)+ CO(g)➔CN4(g) + H2O(g)
∆H = -51 kJ
∆H favours products
∆S favours reactants
therefore the rx ________________
3H2(g)+ CO(g)➔CN4(g) + H2O(g)
∆H = -51 kJ
∆H favours products
∆S favours reactants
therefore the rx goes to equilibrium
H2O(l)+ heat➔ H2O(g)
∆H favours___________
∆S favours___________
therefore the rx ________________
H2O(l)+ heat➔ H2O(g)
∆H favours reactants
∆S favours products
therefore the rx ________________
H2O(l)+ heat➔ H2O(g)
∆H favours reactants
∆S favours products
therefore the rx goes to equilibrium
Do: 14 - 16
