topic 6 Flashcards
for a chemical reaction to occur particles must : (2)
- collide in the correct orientation
- with enough energy for a reaction to take place called the activation energy
what is the rate of reaction
the speed at which the reaction takes place
ways to speed up chemical reactions
- lower volume (increase pressure)
- increase number of particles
- increasing temperature
- increasing surface area
- using a catalyst
what does increasing concentration mean, and how is it achieved
increases number of solute particles per unit volume, achieved by adding more particles
what does increasing the concentration do in terms of particles
increases the frequency of collisions and rate of reaction
what does increasing pressure mean, and how is it achieved
increases the number of gas particles per unit volume. achieved by adding particles or reducing container volume
what does increasing pressure do in terms of particles
increases the frequency of collision and rate of reaction
what does increasing temperature do do particles
increases the kinetic energy allowing more particles to collide more frequently and with enough energy to overcome the activation energy,
what does increasing surface area mean
means more particles are exposed on the outside, fewer unexposed particles in the middle.
what are catalysts and what do they do to rate of reaction in chemistry
are chemicals that speed up the rate of reaction without being used up or changing at the end of the reactions. they do this by allowing the reactant particles to collide more easily making the collisions more successful
what happens to the rate of reaction as reactions take place
rate of reaction decreases because as more products are formed, concentration of reactants decrease.
what happens to bonds when making new particles
bonds between reactant particles must be broken
about an endothermic reaction
- energy, bonds, temp
- absorbing energy
- breaking bonds = absorbing energy
- temperature of surrounding decreases
about an exothermic reaction
- energy, bonds, temp
- involves releasing energy
- making bonds = releasing energy
- temperature of surroundings increase
what does it mean in terms of bonds when a overall reaction is exothermic
energy absorbed to break bonds < energy released to make bonds
what does it mean in terms of bonds when a overall reaction is
endothermic
energy absorbed to break bonds > energy released to make bonds
what is enthalpy , and units
the change in energy between reactants and products
kj/mol or kj mol -1
enthalpy equation
total energy of bonds broken - total energy of bonds made
what is a negative and positive enthalpy
positive - endothermic
negative - exothermic
a reversible reaction can only occur if ..
the product or reactant is not limiting or limited by a limiting factor
definition of equilibrium
- rate of forward and reverse reaction is equal
- the concentration of the reactant(s) and product(s) remain constant
- requires a closed system where no matter can escape or be introduced
what is Le Chatelier’s principle
any change to an equilibrium will eventually return to equilibrium
what does increasing temp favour and what does decreasing temp favour
increase favours endothermic
decrease favours exothermic
what does increasing concentration favour and what does decreasing concentration favour
increase reactants favours products/ forward reaction
increase products favours reactants / reverse reaction
what does increasing pressure favour and what does decreasing pressure favour
increase favours side with less moles
decrease favours side with more moles
what does adding a catalyst do to equilibrium position do
nothing, both forward and reverse reaction are being sped up equally
what is the haber process used for
used to manufacture ammonia to produce nitrogen based fertilizers
haber process symbol equaion
N2 (g) + 3H2 (g) -> 2NH3 (g)
enthalpy of
haber process, endo or exo, enthalpy value
-92 kj mol -1 , exothermic
raw materials in haber process
nitrogen from air, hydrogen from natural gas (methane)
conditions needed for haber process
iron catalyst , high temperature, high pressure
what happens at the end of haber process
on cooling ammonia is liquified and removed so that it doesnt break down again
best temp for haber process and why
450 oC , a compromise as it provides best rate of reaction and yield.
best pressure for haber process, why
200 atm, safer and saves money
raw materials in the contact process
sulfur , air , and water
conditions needed for contact process
vanadium oxide (V2O5) catalyst, 450 oC, 2 atm
symbol equation for the conversion of sulfur dioxide to sulfur trioxide in the contact process
2SO2 (g) + O2 -> 2SO3 (g)
steps in contact process (3)
1 sulfur is burned in air to produce sulfur dioxide
2. sulfur dioxide reacts with air with the presence of a vanadium oxide catalyst to form sulfur trioxide
3. sulfur trioxide mixed with dilute sulfuric acid to produce oleum,
oleum mixed with water to produce sulfuric acid.
why is the specific temp used in the contact process
catalyst doesn’t work below 400 oC, high temp decreases yield but low temp gives low rate of reaction
enthalpy of main contact process reaction
- 196 kj mol -1
why is a moderate pressure used in the contact process
position of equilibrium already favours the right (bc lower moles) so high pressure is too expensive and not needed.
sources of sulfur
volcanoes , metal ores, fossil fuels
uses of sulfuric acid
fertilisers , manufacture of chemicals, processing metal, batteries
properties of sulfuric acid
strong acid, corrosive, good electrolyte , dehydrating agent.
