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reaction rate =
amount of product formed or reactant used divided by time interval
Concentration of reactants
decrease because gets used up.
Concentration of products
increase because is formed.
evidence of a chemical reaction taking place
new gas formed (bubbles), solid. disappearing
Activation Energy
(Ea) minimum amount of energy required for a reaction to occur
Activated Complex
high energy arrangement of reactant molecules where molecules have enough energy to continue reaction
Catalyst
substance that speeds up a chemical reaction without being consumed itself
particle size (s) = more surface area = increased rate
more places where molecules able to make contact or collisions
increased concentration =
more molecules in solution and available for collisions (s, l, g particles and aq molarity)
chemical make-up of, nature of reactants
reactivity trends or number of bonds to break and form
increased temperature =
increase in number of molecules in solution, collisions, in rate
Catalyst
increase rate by lowering activation energy so more molecules have enough energy to react
Reaction Mechanism
sequence of steps in a chemical reaction
Rate-Determining Step
slowest reaction in Reaction Mechanism, determines rate of overall reaction
rate of the forward reaction is equal to
rate of reverse reaction
not included as part of the equilibrium expression
solid and liquid because densities do not change
if gas is produced
collect the gas then measure pressure, volume, mass
if reaction involves solutions
may have color change
if reaction involves solids
measure decrease of a mass solid reactant OR increase of a solid product
properties of a catalyst
high activity, high selectivity, and stability over time
increase rate of reaction of a solid (molecular)
grind into powder increase surface, collisions, rate
increase rate of reaction aqueous (molecular)
increase concentration which increases number of molecules in a solution, collisions, rate
increase rate of reaction temperature (molecular)
increase temperature which increases KE of molecules, velocity, collision, rate
increase rate of reaction catalyst (molecular)
add a catalyst lowers activation energy so more molecules have energy to react
← K increases
product ↑
→ K decreases
reactant ↑
← increase in pressure
V ↓ least space, least number of moles
→ increase in pressure
V ↑ largest moles of gas
rate of the forward reaction and the rate of the reverse reaction
are equal when a reaction has reached equilibrium
pure solids and pure liquids are
NOT included as part of the equilibrium expression
large value for equilibrium constant indicates that
a lot of products are made before reaction reaches equilibrium (products favored)
small value for equilibrium constant indicates that
a lot of reactant are left when reaction reaches equilibrium (reactants favored)
