unit 8 Flashcards
the rate of a chemical reaction measures
how fast the reaction occurs
what happens when a chemical reaction happens at a fast rate?
large fraction of molecules react to form products in a period of time
what happens when a chemical reaction happens at a slow rate?
relatively small fraction of molecules react to form products per unit time
rate definition
change in a quantity (concentration of reactant/product) per unit time
rate (reactant) equation
- (change in concentration) / (change in time)
reactant concentration _ over time
decreases
product concentration _ over time
increases
rate (product) equation
(change in concentration) / (change in time)
what happens to the rate of reaction when a coefficient is before the element/compound in a balanced equation?
multiply the rate by the positive reciprocal of the coefficient
reactant concentration _ with time as reactants are consumed
decreases
product concentration _ with time as products are formed
increases
4 factos that affect the rate of the reaction
physical state
reactant concentration
reaction temp
presence of a catalyst
the more readily reactant molecules collide with each other, the more _ they react
rapidly
reactant concentration and reaction rate proportion
directly proportional
temp and reaction rate proportion
direct (generally)
catalyst definition
agents that increase reaction rates without themselves being used up
2 methods of measuring reaction concentrations
spectroscopy
monitoring the pressure of gases
how to measure the reactant concentrations from spectroscopy:
measure the change in absorbance of light
calculating concentration using beer’s law
rate law definition
relationship between rate of reaction and concentration of the reactant
rate law formula
rate = k[A]^n
k: rate constant
n: reaction order
zero order reaction
n = 0
-molarity of reactant decreases linearly
-reaction does not slow down as [A] decreases
-rate order is the same at any [A]
-amount of reactant available for reaction is unaffected by overall quantity of reactant
first order
n = 1
-rate slows as reaction proceeds
-rate is slower as reaction proceeds
-rate is directly proportional to concentration
second order
n = 2
-rate is proportional to the square of [reactant]
-rate is more sensitive to [reactant]
-rate slows faster than first order reaction
the order of a reaction can only be determined by _
experiment