x Flashcards
what is meant by rate of reaction?
change in concentration of a reactant or a product in a given time
write an equation for the rate of reaction
rate= change in concentration/ time
what as the units for the rate of reaction?
moldm⁻³s⁻¹
state 5 factors that can affect the rate of reaction.
- concentration
- pressure
- catalyst
- temperature
- surface area
why are some collisions effective?
- correct orientation
- sufficient energy to overcome activation energy
how does increasing the concentration affect the rate of reaction?
- increases the number of particles in the same volume
- collide more frequently and closer together
- increases the rate of reaction
how does increasing the pressure of a gas affect the rate of reaction?
- the same number of particles but in a smaller volume
- closer together and collide more frequently
- increases the rate of reaction
2 methods of measuring progress of a chemical reaction
- monitoring the removal (decrease in concentration) of a reactant
- following the formation (increase in concentration) of a product
state 2 possible methods for monitoring the rate of reactions that produce gases
- monitoring the volume of gas produced at regular time intervals using gas collection
- monitoring the loss of reactants using a balance
what is a catalyst?
alters the rate of reaction without being used up
what effect does a catalyst have on the rate of a reaction?
- speeds up a reaction
- provides an alternative route
- catalyst is regenerated
- catalyst may react with a reactant to form an intermediate
complete an enthalpy profile diagram of an exothermic reaction, with and without a catalyst
see page 149
complete an enthalpy profile diagram of an endothermic reaction, with and without a catalyst
see page 149
what is a homogenous catalyst?
same physical state as the reactants
give 2 examples of homogenous catalysts with equations
- making esters with H₂SO₄
C₂H₅OH(l) + CH₃COOH(l)→ CH₃COOC₂H₅(l) + H₂O (l) - ozone depletion with Cl• (g)
2O₃ (g) → 3O₂ (g)
what is a heterogeneous catalysts?
different physical state from the reactants
give 2 examples of heterogeneous catalysts with equations
- making ammonia (Haber process) with Fe(s)
N₂ (g) +3H₂ (g) →2NH₃ (g) - making SO₃ (g) (contact process) with V₂O₅ (s)
2SO₂ (g) + O₂ (g) → 2SO₃ (g)
why do catalysts have great economic importance and benefits?
increased sustainability by lowering temperatures and reducing energy demand from combustion of fossil fuels with resulting reduction in CO₂ emissions
the effect of temperature on the Boltzmann distribution
- area under curve exceeding Ea = number of molecules that can react
- at higher temperature, area under curve > Ea is greater so more can react
State two characteristics of a dynamic equilibrium.
- rate of forward reaction= rate of reverse reaction
- concentrations of reactants and products do not change
le Chatelier’s principle
when a system in equilibrium is subjected to an external change the system readjusts itself to minimise the effects of that change
