Chemical Change: Energy, Rate and Equilibrium Thermodynamics: study of energy, work and heat Kinetic...
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Transcript of Chemical Change: Energy, Rate and Equilibrium Thermodynamics: study of energy, work and heat Kinetic...
![Page 1: Chemical Change: Energy, Rate and Equilibrium Thermodynamics: study of energy, work and heat Kinetic energy: energy of motion Potential energy: energy.](https://reader034.fdocuments.in/reader034/viewer/2022051301/5a4d1b127f8b9ab05998ffd8/html5/thumbnails/1.jpg)
Chemical Change: Energy, Rate and Equilibrium
Thermodynamics: study of energy, work and heat
Kinetic energy: energy of motion
Potential energy: energy of position, stored energy
Chemical reactions involve changes in energy.
Types of energy include:
Heat, sound, electricity, light, motion, etc.
Example: 2H + O2 2H2O + energy
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Exothermic Reaction: Reaction that releases heat to surroundings
Endothermic Reaction: Reaction that absorbs heat from surroundings
Exothermic Rxn Endothermic Rxn
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Practice:
Identify each reaction as 1) exothermic or 2) endothermic
A. N2 + 3H2 2NH3 + 22 kcal
B. CaCO3 + 133 kcal CaO + CO2
C. 2SO2 + O2 2SO3 + heat
Exo
Exo
Endo
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1st law of thermodynamics: energy of the universe is constant
Enthalpy: heat energy; change in heat energy from reactants to products is Ho
Spontaneous Process: Process that takes place without persuasion, without stimulus or energy input (Ball rolling downhill)
Nonspontaneous Process: Process that requires energy or stimulus to occur (Ball being pushed uphill)
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Entropy: Measurement of disorder or randomness of a system; change in entropy from reactants to products is DSo
2nd law of thermodynamics: entropy of universe spontaneously tends to increase
Kinetics
Kinetics: study of the rate, or speed of chemical reactions
Reaction Rate: Speed of a reaction; how quickly or slowly a reactant is used up or a product accumulates
Activation energy: minimum amount of energy required to produce a chemical reaction
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Note the Activation Energy (Ea) in Exothermic and Endothermic Rxns
Exothermic Rxn Endothermic Rxn
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Factors that Influence Reaction Rates
Structure of Reactants
Attraction between oppositely charged particles; breaking of covalent bonds; size of molecules
Concentration of Reactants
The greater the concentration of reactants, the more collisions leading to a reaction will occur
Temperature of Reactants
Increasing the temperature increases the kinetic energy of the particles, allowing more collision to occur
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Physical state of Reactants
Solid, liquid or gas
Presence of Catalysts
Catalyst: Substance that increases rate of a reaction without being used up in the reaction
Catalysts provide alternate way for reaction to occur, with a lower activation energy than the normal way
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Effect of Catalyst on Activation Energy
Without Catalyst
(High Ea)
With Catalyst
(Lower Ea)
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Chemical Equilibrium
Chemical reactions can go both directions
H2 + I2 2HI
Equilibrium: Condition when rate of forward reaction equals rate of reverse reaction
Equilibrium Concentrations: Unchanging concentrations of products and reactants in a reaction that is at equilibrium
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Equilibrium Position Can Change!
H2 + I2 2HI
Le Chatelier’s Principle: Equilibrium position will shift in response to changing conditions in such a way as to minimize or oppose changes
Note: Concentration of chemicals and heat will affect equilibrium; presence of a catalyst will not!
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Summary of Changes on Equilibrium