Rates of Reaction and Equilibrium . Rates of reaction = kinetics Equilibrium = balance . To react, atoms must get together: . Called the collision theory: Students act a chemical reaction 1. 2. 3. . To react, atoms must: . 1. Get together (collide)
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1. Get together (collide)
2. Get together in the right way (orientation)
Collide with the “correct” side of a molecule
NO₂ + CO ↦ NO + CO₂
Carbon must hit the O side of NO₂ to get one of the O from the NO.
3. Get together with enough energy (force) so that the electrons can be shared/transferred
Reaction rate of a chemical reaction:
measured by change in concentration per unit time
5 FACTORS AFFECTING REACTION RATES
3 factors relate to energy
2 factors relate to the particles
Why? *particles move faster and collide with greater intensity
2. agitation: increases reaction rate
Why? *increases likelihood of particles being exposed to one another; increase in collisions
examples: shaking, stirring
3. catalysts: substance that increases the reaction rate without being used up in the reaction.
Why? * lowers the ACTIVATION energy;
sort of “invites” reacting particles together so they will react
Why? *increasing # particles increases chance of collision resulting in a reaction
Why? *greater exposure of reacting particles to each other
examples: pulverizing, crushing, chopping up, etc
Example: Logs vs. twigs
Chemical Equilibrium = Balance
Products recombine to form the original substances .
Needs a closed system: no additional reactants added and no products are taken away or escape as a gas)
Dynamic equilibrium Forward and backward reactions taking place at the same rate
Upsetting the equilibrium = shifting the equilibrium
If an endothermic reaction -absorb or release heat?
-example of types of reaction?
CaCO₃ + heat ⇄ CaO + CO₂
Add more heat (raise the temperature) to make more product
If an exothermic reaction– reduce the amount heat (lower the temperature) to make more product
Reaction will try to replace the heat that was taken away
If we increase the pressure –
The reaction will “favor” the reaction side with less volume
If we lower the pressure –
The reaction will “favor” the reaction side with more volume
N₂ + 3 H₂ ⇄ 2NH₃
Add coefficients at exponents
Will use equilibrium constant when determining pH and pOH
Exothermic chemical reaction
Endothermic chemical reaction