kinetics Flashcards
(31 cards)
state when reactions occur?
when collisions take place between particles with sufficient energy to break the bonds in the correct orientation
what 2 factors does the rate depend on?
frequency of collisions and success of collisions
in order to increase the rate of reaction we need to increase the number of ……?
succesful collisions
what are 4 things we can add/change to influence the rate?
add catalyst, change temp, pressure, surface area
how can an increase in concentration increase pressure ?
more particles present in a given volume so increase in pressure
define activation energy
minimum energy needed to start a reaction
define rate of reaction
speed at which a chemical reaction takes place
state rate of reaction units
mol dm^-3 s^-1
state what an ineffective collision is
when particles collide in wrong orientation or not enough energy to bounce off each other without causing a reaction
state the meaning of collision frequency ?
number of collisions per unit time
why does a Maxwell boltzsman start at the origin ?
no particles have zero energy
what and where is the most probable energy on a Maxwell boltzsman and why?
the energy that most particles have, at the peak on the curve because that is where most particle are
what does the area under the curve of a Maxwell boltzsman represent ?
number of particles
label the y and x axis on a Maxwell boltzsman graph
y- number of particles / molecules
x- energy
where would the mean energy be on a Maxwell boltzsman graph ?
to the right of the peak because there are some particle that have higher energy that the MPE which brings the average up
what happens to a Maxwell boltzsman distribution when temperature is lowered ?
area under curve stays same
peak moves left (lower energy )
peaks gets higher and more particles having less energy
what happens to a Maxwell boltzsman distribution when temperature is increased ?
peak gets higher and lower
in an exothermic reaction do particles or reactants have higher energy?
reactants
in an endothermic reaction do particles or reactants have higher energy?
products
what does an increase In reaction rate mean for the Ea?
greater proportion of molecules have energy equal or higher than Ea
how does a catalyst increase rate if reaction ?
provides an alternate pathway for a reaction, one which has lower Ea. it is chemically unchanged
what effect does increasing concentration have on the rate of reaction ?
more particles in a given volume in the higher concentration solution therefore increasing the number of successful collisions and increasing the rate of reaction
what effect does increasing temperature have on the rate of reaction ?
particles have higher kinetic energy so more frequent collisions and increases rate of reaction
what effect does increasing pressure have on the rate of reaction ?
particles closer and collide more often (more frequent collisions) so a higher chance of a reaction starting