rate of reaction Flashcards
what is the definition of rate of reaction
-measures how fast a reactant is used up or how fast a product is formed
-or the change in concentration of a reactant over time
how to measure rate of reaction for concentration
change in concentration/ time
what factors affect rate of reaction
-temperature
-catalyst
-surface area
-concentration or preassure
what is the collision theory
two reacting particles have to collide for a reaction to occur
what is an effective collision
a collision that leads to a chemical reaction
what factors lead to an effective collision
-the particles have to collide with the correct orientation
-particles have sufficient energy to overcome the activation energy barrier of the reaction
how does increasing concentration lead to faster rate of reaction
-increases number of particles in same volume
-particles closer together and collide more frequently
-more effective collisions with correct orientation and activation energy
how does increasing preassure increase rate of reaction
-concentration of gas molecules increases as the volume the gas molecules are in is smaller
-molecles closer together and collide with correct orientation and sufficient energy
how to measure change in concentration
-monitoring decrease in concentration of reactants during reaction
-monitoring increase in concentration of products during reaction
what two methods are used to determine rate of reaction of gases
-monitoring volumes of gas at regular intervals using gas collection
-monitoring loss of mass of reactants using mass balance
what is a catalyst
- substance that changes the rate of a chemical reaction without being permanently changed
-provides an alternate reaction pathway to lower the activation energy
what two ways does catalysts speed up reactions
-provides a surface on which the reaction can take place
- react with the reactants to form an intermediate
draw an exothermic and endothermic enthalpy graph with and without a catalyst
what is a homogeneous catalyst
-has the same physical state as the reactants
how does homogeneous catalysts work
-reacts with reactants to form an intermediate which breaks down to give product and the catatylst
what is a heterogeneous catalyst
-different physical state from the reactants
how does heterogenous catalysts work
-reactant molecules absorbed into the surface of the catalyst
-reaction takes place at the surface of catalyst
-product molecules leave surface of catalyst by desorption
give 3 examples of reactions and their heterogeneous catalyst
-haber process (making ammonia)—> Fe (s)
-reforming–> Pt / Rh
-hydrogenation of alkenes–> Ni
how much chemical materials are produced using a catalyst
90%
why are catalysts sustainable
-lower activation energy
-reduces temperature and energy requirements needed for the process
-less energy–> less fossil fuels burned/less electricity used
-reduced CO2 emmisisons
why are catalysts recycled
-many catalysts contain toxic compounds–> may leech into soil if sent to landfill
-may contain valuable metals like platinum
how is the decision to recycle the catalyst or send it to landfill made
-balancing the economic and environmental factors
how do molecules in a gas move
-high speed
-collide with each other and the container they are in
-collisions are elastic–> do not slow down because of the collision and no energy lost
what is the Boltzmann
distribution
The spread of molecular energies in gases
