kinetics Flashcards
(22 cards)
collision theory
reactions can only occur when collisions take place between particles having sufficient energy
factors that affect the rate of reaction
temperature, pressure, concentration, surface area and catalysts
3 factors rate of a chemical reaction depends on
collision frequency, collision energy, activation energy
what factors can affect collision frequency
concentration, pressure, temperature or size of particles
when do unsuccessful collisions happen
when colliding species do not have enough energy to break the necessary bonds
what is activation energy
minimum energy the colliding particles need in order to react
what does increasing concentration do
- increases numbers of particles per unit volume
- more successful collisions
- increase the rate of reaction
what does increasing pressure (in gases) do
- decreases the volume
- increases number of particles per unit vol
- more successful collisions
- increasing rate of reaction
increasing surface area
- more successful collisions per unit time
- increasing the rate of reaction
increasing temp
- means particles have more energy than activation energy
- increases collision frequency
- increases rate of reaction
- kinetic energy of all molecules increases
how does catalyst increase reaction rate
provides an alt route with a lower activation energy
lower activation energy means particle energy > activation energy
more successful collisions
2 reasons why majority of molecular collisions do not result in reaction
- because the activation energy is higher than the collision energy
- colliding particles end up bouncing off eachother
rate of reaction meaning
change in concentration in given time
why is the most probable energy of molecules in a sample is not the same as average energy of molecules in the same sample
because most probable is determined by the peak of the maxwell-boltzmann distribution curve whilst the average energy is determined by the area under the curve
how can we measure the rate of reaction
volume of gas produced
change in mass
colour change
formation of precipritate
how could you find the curve on a graph
gradient
why is it important to clean the surface of magnesium ribbon when investigating the rate of reaction
bc its coated in an oxide
difference between mg reacting with hot water and mg reacting with steam
hot water: produces magnesium hydroxide
steam: bright white light, white solid
pure mg reacts wth excess so4 and pure ca reacts with excess excess so4 but not all ca reacted, why?
because mg sulfate is soluble whilst ca sulfate is insoluble. caso4 coats the surface of ca and prevents further contact with acid
why is 1/t used
measured change is fixed
explain why the slope of curve decreases as time increases
because reactant falls
where will the graph shift when the temp is higher
it will shift to the right
