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II.3 Predicting Whether a Rx is Spontaneous or Not p

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Spontaneous a change that occurs by itself, without any help some rxs are spontaneous, others are not

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Enthalpy H (heat) systems drive towards the lowest possible energy state endothermic rx = +H exothermic rx = -H

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Entropy S possibility for disorder, the drive towards randomness increasing entropy = +S decreasing entropy = -S

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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)

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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

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Ex. of Minimum Enthalpy: PE Time Exo favours products

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Ex. of Minimum Enthalpy: PE Time Exo favours products PE Time Endo favours reactants

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic favours _______ (+) favours _______ (-) exothermic favours _______ (-) favours _______ (+) endothermic favours _______ (+) favours _______ (+) endothermic favours _______ (-) favours _______

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic Favours products (+) favours products (-) exothermic favours _______ (-) favours _______ (+) endothermic favours _______ (+) favours _______ (+) endothermic favours _______ (-) favours _______

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic Favours products (+) favours products Spontaneous Rx goes 100% (-) exothermic favours _______ (-) favours _______ (+) endothermic favours _______ (+) favours _______ (+) endothermic favours _______ (-) favours _______

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic Favours products (+) favours products Spontaneous Rx goes 100% (-) exothermic favours products (-) favours reactacts (+) endothermic favours _______ (+) favours _______ (+) endothermic favours _______ (-) favours _______

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic Favours products (+) favours products Spontaneous Rx goes 100% (-) exothermic favours products (-) favours reactacts Spontaneous Rx goes to Equil. (+) endothermic favours _______ (+) favours _______ (+) endothermic favours _______ (-) favours _______

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic Favours products (+) favours products Spontaneous Rx goes 100% (-) exothermic favours products (-) favours reactacts Spontaneous Rx goes to Equil. (+) endothermic favours reactants (+) favours products (+) endothermic favours _______ (-) favours _______

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic Favours products (+) favours products Spontaneous Rx goes 100% (-) exothermic favours products (-) favours reactacts Spontaneous Rx goes to Equil. (+) endothermic favours reactants (+) favours products Spontaneous Rx goes to Equil. (+) endothermic favours _______ (-) favours _______

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic Favours products (+) favours products Spontaneous Rx goes 100% (-) exothermic favours products (-) favours reactacts Spontaneous Rx goes to Equil. (+) endothermic favours reactants (+) favours products Spontaneous Rx goes to Equil. (+) endothermic favours reactants (-) favours reactants

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The Probability of a Rx Occuring: HSSpontaneity (-) exothermic Favours products (+) favours products Spontaneous Rx goes 100% (-) exothermic favours products (-) favours reactacts Spontaneous Rx goes to Equil. (+) endothermic favours reactants (+) favours products Spontaneous Rx goes to Equil. (+) endothermic favours reactants (-) favours reactants Rx will NOT occur

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Ex: 2NH 3(g) + 92 kJ N 2(g) + 3H 2(g) H favours___________ S favours___________ therefore the rx ________________

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Ex: 2NH 3(g) + 92 kJ N 2(g) + 3H 2(g) H favours reactants S favours products therefore the rx ________________

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Ex: 2NH 3(g) + 92 kJ N 2(g) + 3H 2(g) H favours reactants S favours products therefore the rx goes to equilibrium

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BaCO 3(s) BaO (s) + CO 2(g) H=600kJ H favours___________ S favours___________ therefore the rx ________________

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BaCO 3(s) BaO (s) + CO 2(g) H=600kJ H favours reactants S favours products therefore the rx ________________

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BaCO 3(s) BaO (s) + CO 2(g) H=600kJ H favours reactants S favours products therefore the rx goes to equilibrium

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3H 2(g) + CO (g) CN 4(g) + H 2 O (g) H = -51 kJ H favours___________ S favours___________ therefore the rx ________________

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3H 2(g) + CO (g) CN 4(g) + H 2 O (g) H = -51 kJ H favours products S favours reactants therefore the rx ________________

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3H 2(g) + CO (g) CN 4(g) + H 2 O (g) H = -51 kJ H favours products S favours reactants therefore the rx goes to equilibrium

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H 2 O (l) + heat H 2 O (g) H favours___________ S favours___________ therefore the rx ________________

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H 2 O (l) + heat H 2 O (g) H favours reactants S favours products therefore the rx ________________

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H 2 O (l) + heat H 2 O (g) H favours reactants S favours products therefore the rx goes to equilibrium

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