Rates Of Reaction Flashcards
Define rate of reaction
The rate of a reaction measures how quickly a reactant is used up or how quickly a product is formed
Model used to explain how different factors affect the rate of a reaction
Collision Theory
What must take place for a reaction to happen?
- reactant particles must collide with each other
(particles=face correct direction) - the particles must have enough energy for them to react
Name for collision that produces a successful reaction
Successful collision
Minimum amount of energy needed for a collision to be successful
Activation Energy
calculate mean rate of reaction (when you can measure product)
Mean Rate of Reaction= Quantity of Product Formed / Time Taken
calculate mean rate of reaction (when you can measure reactant)
Mean Rate of Reaction= Quantity of Reactant Used / Time Taken
Measuring mass- rate units
g/m or g/s
When is measuring mas useful?
When CO2 is a product which leaves the reaction container
Measuring volume- rate units
cm3 s-1 or cm3 min-1
When is measuring mass NOT useful?
When gas that leaves= small relative mass (i.e. H2)
When is measuring volume useful?
When gas leaves reaction container.
How is volume of gas measured?
-gas syringe OR -upside down burette OR -measuring cylinder
GRAPHS- STEEP CURVE VS NOT
the steeper the line, the faster the reaction
fast reactions finish faster than slow ones (seen when line goes horizontal.
INCREASE in concentration=?
higher FREQUENCY of successful collisions
= higher reaction rate)(mean energy NO change
INCREASE pressure=?
higher FREQUENCY of successful collisions
= higher reaction rate)(mean energy NO change
What happens when lump is divided?
- total volume is same
- surface area increases
- surface area to total volume rate increases
LARGER SURFACE ARE=?
higher FREQUENCY of successful collisions
= higher reaction rate)(mean energy NO change
HIGHER TEMPERATURE=?
higher FREQUENCY of successful collisions as
-particles move more quickly
-energy of particles increases
= PROPORTION of successful collisions increases
(and reaction rate increases)
WHAT DOES A CATALYST DO?
- speed up rate of reaction
- does NOT alter the products of a reaction
- is NOT chemically changed or used up in end
how much mass of catalyst is needed to speed up reaction?
small amount
How do catalysts work?
- provides alternative reaction pathway w/lower activation energy than uncatalysed reaction
- DOES increase frequency of successful collisions
- This is because as energy required= lower, more particles have necessary amount of activation energy
Decreasing particle size of reactant=?
-increasing surface area
=higher rate of reaction
